Organic semiconductor compositions

ABSTRACT

The present invention relates to organic copolymers and organic semiconducting compositions comprising these materials, including layers and devices comprising such organic semiconductor compositions. The invention is also concerned with methods of preparing such organic semiconductor compositions and layers and uses thereof. The invention has application in the field of printed electronics and is particularly useful as the semiconducting material for use in formulations for organic thin film transistor (OFET) backplanes for displays, integrated circuits, organic light emitting diodes (OLEDs), photodetectors, organic photovoltaic (OPV) cells, sensors, memory elements and logic circuits.

This application is a continuation of U.S. patent application Ser. No.14/379,773, filed Aug. 20, 2014, which is a national phase applicationunder 35 U.S.C. §371 of International Application No. PCT/GB2013/050457,filed Feb. 25, 2013, which claims the benefit of priority to UnitedKingdom Patent Application No. 1203159.7, filed Feb. 23, 2012. Theentire contents of the above-referenced disclosures are specificallyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to organic copolymers and organicsemiconducting compositions comprising these materials, including layersand devices comprising such organic semiconductor compositions. Theinvention is also concerned with methods of preparing such organicsemiconductor compositions and layers and uses thereof. The inventionhas application in the field of printed electronics and is particularlyuseful as the semiconducting material for use in formulations fororganic field effect transistor (OFET) backplanes for displays,integrated circuits, organic light emitting diodes (OLEDs),photodetectors, organic photovoltaic (OPV) cells, sensors, memoryelements and logic circuits.

BACKGROUND OF THE INVENTION

In recent years, there has been an increasing interest in organicsemiconducting materials as an alternative to conventional silicon-basedsemiconductors. Organic semiconducting materials have several advantagesover those based on silicon, such as lower cost, easier manufacturing,solution processability at low temperatures as well as increasedflexibility, mechanical robustness, good compatibility with a widevariety of flexible substrates and light weight. They thus offer thepossibility of producing more convenient high performance electronicdevices.

Polyacene compounds and their analogues in particular have shown promisein this field of technology. WO 2005/055248 for example, discloses anorganic semiconducting layer formulation comprising an organic binderwhich has a permittivity (E) at 1000 Hz of 3.3 or less, and a polyacenecompound. However the method for preparing the OFETs described in WO2005/055248 in practice is limited and is only useful for producing topgate OFETs having relatively long channel lengths (typically >50microns). A further disadvantage of WO 2005/055248 that is overcome bythe present invention, is that it frequently uses undesirablechlorinated solvents. The highest performance semiconductor compositionsdisclosed in WO 2005/055248 having mobilities≧1.0 cm²V⁻¹s⁻¹,incorporated 1,2-dichlorobenzene as the solvent (page 54, Table 5 andexamples 14, 21 and 25). Moreover these solvents are not ones that wouldbe industrially acceptable in a printing process and these are alsodamaging to the environment. Therefore it would be desirable to use morebenign solvents for the manufacture of these semiconductor compositions.Furthermore, it is generally thought that only polymer binders with apermittivity of less than 3.3 could be used since any polymers with ahigher permittivity resulted in a very significant reduction in mobilityvalues of the OFET device.

This reduction in mobility value can further be seen in WO 2007/078993which discloses the use of 2,3,9,10-substituted pentacene compounds incombination with insulating polymers having a dielectric constant at1000 Hz of greater than 3.3. These compounds are reported to exhibitmobility values of between 10⁻² and 10⁻⁷ cm²V⁻¹s⁻¹ which are too low tobe industrially useful.

Therefore, the present invention seeks to provide organic semiconductorcompositions, which overcome the above-mentioned problems, by providingsolvent soluble, high mobility, high flexibility polycyclic aromatichydrocarbon copolymers, especially polyacene copolymers and polyaceneanalogue copolymers having a tunable permittivity value and whichexhibit high mobility values.

SUMMARY OF THE INVENTION

The copolymers and compositions of the invention are expected to producesoluble materials that, on deposition, afford flexible, non-brittlelayers unlike layers made from solely small molecule compounds. Thecopolymers of this invention have significantly higher mobilities thantypical semiconducting binders used in the field of printableelectronics, such as the polytriarylamine class of semiconductingbinders that have mobilities in the order of ˜10⁻⁶ to 10⁻³ cm²/Vs. Thecopolymers of the invention will be industrially useful in thefabrication of rollable and flexible electronic devices such as OTFTarrays for displays; large area printed sensors and printed logic. Inparticular, the semiconducting polymers of this invention will be usefulin formulations for organic thin film transistors (OTFTs) having shortchannel lengths (≦30 microns and even ≦5 to 10 microns) that may be usedas the backplane driver for electrophoretic displays, high resolutionLCD and AMOLED displays.

The copolymers are also soluble in benign, non-chlorinated solvents,such as those typically used in printing.

The present invention also provides highly flexible, non-brittle,semi-conducting films.

Polycyclic Aromatic Hydrocarbon Copolymers

Polycyclic Aromatic Hydrocarbon Copolymers (hereinafter PAHCs) accordingto the present invention comprise a mixture of at least one polyacenemonomer unit having the Formula (A) and at least one triarylaminemonomer unit having the Formula (B)

wherein each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³and R¹⁴, which may be the same or different, independently representshydrogen; a branched or unbranched, substituted or unsubstituted C₁-C₄₀alkyl group; a branched or unbranched, substituted or unsubstitutedC₂-C₄₀ alkenyl group; a branched or unbranched, substituted orunsubstituted C₂-C₄₀ alkynyl group; an optionally substituted C₃-C₄₀cycloalkyl group; an optionally substituted C₆-C₄₀ aryl group; anoptionally substituted C₁-C₄₀ heterocyclic group; an optionallysubstituted C₁-C₄₀ heteroaryl group; an optionally substituted C₁-C₄₀alkoxy group; an optionally substituted C₆-C₄₀ aryloxy group; anoptionally substituted C₇-C₄₀ alkylaryloxy group; an optionallysubstituted C₂-C₄₀ alkoxycarbonyl group; an optionally substitutedC₇-C₄₀ aryloxycarbonyl group; a cyano group (—CN); a carbamoyl group(—C(═O)NR¹⁵R¹⁶); a carbonyl group (—C(═O)—R¹⁷); a carboxyl group(—CO₂R¹⁸) a cyanate group (—OCN); an isocyano group (—NC); an isocyanategroup (—NCO); a thiocyanate group (—SCN) or a thioisocyanate group(—NCS); an optionally substituted amino group; a hydroxy group; a nitrogroup; a CF₃ group; a halo group (Cl, Br, F, I); —SR¹⁹; —SO₃H; —SO₂R²⁰;—SF₅; an optionally substituted silyl group; a C₂-C₁₀ alkynyl groupsubstituted with a SiH₂R²² group, a C₂-C₁₀ alkynyl substituted with aSiHR²²R²³ group, or a C₂-C₁₀ alkynyl substituted with a—Si(R²²)_(x)(R²³)_(y)(R²⁴)_(z) group;wherein each R²² group is independently selected from the groupconsisting of a branched or unbranched, substituted or unsubstitutedC₁-C₁₀ alkyl group, a branched or unbranched, substituted orunsubstituted C₂-C₁₀ alkynyl group, a substituted or unsubstitutedC₂-C₂₀ cycloalkyl group, a substituted or unsubstituted C₂-C₁₀ alkenylgroup, and a substituted or unsubstituted C₆-C₂₀ cycloalkylalkylenegroup;each R²³ group is independently selected from the group consisting of abranched or unbranched, substituted or unsubstituted C₁-C₁₀ alkyl group,a branched or unbranched, substituted or unsubstituted C₂-C₁₀ alkynylgroup, a substituted or unsubstituted C₂-C₁₀ alkenyl group, asubstituted or unsubstituted C₂-C₂₀ cycloalkyl group, and a substitutedor unsubstituted C₆-C₂₀ cycloalkylalkylene group;R²⁴ is independently selected from the group consisting of hydrogen, abranched or unbranched, substituted or unsubstituted C₂-C₁₀ alkynylgroup, a substituted or unsubstituted C₂-C₂₀ cycloalkyl group, asubstituted or unsubstituted C₆-C₂₀ cycloalkylalkylene group, asubstituted C₅-C₂₀ aryl group, a substituted or unsubstituted C₆-C₂₀arylalkylene group, an acetyl group, a substituted or unsubstitutedC₃-C₂₀ heterocyclic ring comprising at least one of O, N, S and Se inthe ring;wherein x=1 or 2; y=1 or 2; z=0 or 1; and (x+y+z)=3;wherein each of R¹⁵, R¹⁶, R¹⁸, R¹⁹ and R²⁰ independently represent H oroptionally substituted C₁-C₄₀ carbyl or hydrocarbyl group optionallycomprising one or more heteroatoms;wherein R¹⁷ represents a halogen atom, H or optionally substitutedC₁-C₄₀ carbyl or C₁-C₄₀ hydrocarbyl group optionally comprising one ormore heteroatoms;wherein k and 1 are independently 0, 1 or 2;wherein at least two of R¹, R², R³, R⁴, R⁸, R⁹, R¹⁰ and R¹¹ are a bond,represented by

, to another monomer unit having the Formula (A) or (B) and wherein Ar₁,Ar₂ and Ar₃, which may be the same or different, each represent,independently if in different repeat units, an optionally substitutedC₆₋₄₀ aromatic group (mononuclear or polynuclear), wherein preferably atleast one of Ar₁, Ar₂ and Ar₃ is substituted with at least one polar orpolarising groups and for the monomer group (B),

represents a bond to another monomer unit having the Formula (A) or (B).

Preferably, k=1=0 or 1.

Preferably, k=1 and 1=1.

Preferably, x=2 and y=1.

Preferably when z=0, R²² and R²³ together comprise a combination of (i)branched or unbranched, substituted or unsubstituted C₁-C₈ alkylgroup(s) and (ii) branched or unbranched, substituted or unsubstitutedC₂-C₈ alkenyl group(s).

Preferably, any of R²², R²³ and R²⁴ may optionally be substituted with ahalogen atom.

Particularly preferred PAHCs according to the present invention areshown in the following table:

Preferred PAHCs        

Case 1 R^(′a), R^(′b), R^(′c), R^(′d), R^(′e) = H R⁶ = R¹³ =trimethylsilyl ethynyl; R¹, R², R³, R⁴, R⁵, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹²,and R¹⁴ = H; and R³ and, R⁹ are bonds to another unit of Monomer (A) or(B) Case 2 R⁶ = R¹³ = triisopropyllsilylethynyl

Case 4 R⁶ = R¹³ = triisopropyllsilylethynyl; and R¹, R⁴, R⁸, R¹¹ = C₁ toC₄ alkyl (e.g. methyl) Case 5 R⁶ = R¹³ = triisopropyllsilylethynyl; andR¹, R⁴, R⁸, R¹¹ = C₁ to C₄ alkoxy (e.g. methoxy) Case 6 R⁶ = R¹³ =triethylsilylethynyl

Case 1 R^(′b), R^(′d), R^(′e) = H Case 2 Case 3 R^(′a) and R^(′c) = C₁to C₄ alkyl Case 4 Case 5 Case 6 Case 7 Case 1 Case 2 R^(′b), R^(′c),R^(′d), R^(′e) = H Case 3 R^(′a) = C₁ to C₆ alkoxy Case 4 Case 5 (i)R^(′a) = methoxy Case 6 (ii) R^(′a) = ethoxy Case 7 Case 1 R^(′a),R^(′b), R^(′d), R^(′e) = H Case 2 R^(′c) = C₁ to C₆ alkoxy Case 3 Case 4(i) R^(′c) = methoxy Case 5 (ii) R^(′c) = ethoxy Case 6 Case 7 Case 1R^(′a), R^(′b), R^(′c), R^(′d) = H Case 2 R^(′e) = C₁ to C₆ alkoxy Case3 Case 4 (i) R^(′e) = methoxy Case 5 (ii) R^(′e) = ethoxy Case 6 Case 7Case 1 R^(′b), R^(′d), R^(′e) = H Case 2 R^(′a) = R^(′c) = C₁ to C₆alkoxy Case 3 Case 4 (i) R^(′a) = R^(′c) = methoxy Case 5 (ii) R^(′a) =R^(′c) = ethoxy Case 6 Case 7 Case 1 R^(′b), R^(′d) = H Case 2 R^(′a),R^(′c), R^(′e) = C₁ to C₆ Case 3 alkoxy Case 4 Case 5 (i) R^(′a),R^(′c), R^(′e) = methoxy Case 6 (ii) R^(′a), R^(′c), R^(′e) = ethoxyCase 7 Case 1 R^(′b), R^(′d) = H Case 2 R^(′b), R^(′c), R^(′d) = C₁ toC₆ Case 3 alkoxy Case 4 Case 5 (i) R^(′b), R^(′c), R^(′d) = methoxy Case6 (ii) R^(′b), R^(′c), R^(′d) = ethoxy Case 7 Case 1 R^(′b), R^(′c),R^(′d), R^(′e) = H Case 2 Case 3 R^(′a) = Cyano (CN) Case 4 Case 5 Case6 Case 7 Case 1 R^(′b), R^(′c), R^(′d), R^(′e) = H Case 2 R^(′a) =Isopropylcyano group Case 3 Case 4 Case 5 Case 6 Case 7

Case 1 R^(′a), R^(′b), R^(′d), R^(′e) = H Case 2 R^(′c) = Isopropylcyanogroup Case 3 Case 4 Case 5 Case 6 Case 7

The organic semiconductors compounds specified in the table areparticularly preferred as they combine the beneficial properties of highcharge transport mobility (of the binders) with a polarity that is morecompatible with benign, non-chlorinated solvents that will be desirablefor use in large area printing. In addition, as these compounds are morepolar once deposited as the OSC layer, or alternatively as a componentin the OSC layer, they are expected to be resistant to beingre-dissolved by the hydrophobic solvents used for the organic gateinsulators (OGI) such as Cytop. Furthermore, it is expected that thepolar binders are useful for both top gate and bottom gate OTFTs,particularly for bottom gate OTFTs.

The copolymers according to the present invention preferably have anumber average molecular weight (Mn) of between 400 and 100,000, morepreferably between 1600 and 20000, more preferably between 500 and10000, yet more preferably between 450 and 5000, and even morepreferably between 850 and 5000.

The copolymers according to the present invention preferably havebetween 1 and 100000 monomer units having the Formula (A) and between 1and 100000 triarylamine monomer units having the Formula (B). Morepreferably, the copolymers have between 1 and 1000 monomer units havingthe Formula (A) and between 1 and 1000 triarylamine monomer units havingthe Formula (B). More preferably, the copolymers have between 1 and 100monomer units having the Formula (A) and between 1 and 100 triarylaminemonomer units having the Formula (B). Yet even more preferably, thecopolymers have between 1 and 10 monomer units having the Formula (A)and between 1 and 10 triarylamine monomer units having the Formula (B).

Preferably, the organic semiconductor compositions according to thepresent invention contain less than 10% by weight, more preferably lessthan 5% by weight, more preferably less than 1%, more preferably,substantially no organic binders which have a permittivity at 1000 Hz ofless than 3.4.

Preferred PAHCs and compositions of the present invention contain atleast 20 wt. %, more preferably at least 20-40 wt. % (of the total ofall monomer units (A) and (B) in the copolymer or composition) of apolyacene monomer unit having the Formula (A) and at least 20 wt. %,preferably at least 20-80 wt. %, more preferably at least 50 wt. %, andeven more preferably at least 60-80 wt. % of a monomer unit having theFormula (B), more preferably at least 50 wt. % of a monomer unit havingthe Formula (B).

Preferred PAHCs and compositions of the present invention contain atleast 40 wt. % (of the total of all monomer units (A) and (B) in thecopolymer or composition) of a polyacene monomer unit having the Formula(A) and at least 40 wt. %, preferably 60 wt. % of a monomer unit havingthe Formula (B). Preferred PAHCs contain monomer unit (B) as the majorcomponent.

The polyacene copolymers may be produced according to the followinggeneral synthetic regime. For simplicity, a bis(trialkyl)silylsubstituted pentacene is shown (no further substitutions are shown, theskilled person understanding how this can be genericised to thestructures shown above) being coupled to a triphenylamine monomer. Thecoupling reaction is preferably a Yamamoto type coupling (using Nickelchloride, zinc, 2,2′-bipyridyl, triphenylphosphine and dimethylacetamide). However, Suzuki coupling is also possible, although in thiscase it is preferable to remove the boronic esters from the resultingsemiconducting polymer.

wherein α and β are preferably integers of 1-100000; and R has the samedefinition as R²⁵, R²⁶ and R²⁷, as defined below; and R′ is preferably Hor a polar or polarising group as defined below. The halogen end groupsare preferentially reacted either by substitution or hydrogentation.

wherein α and β are preferably integers of 1-100000; and R has the samedefinition as R²⁵, R²⁶ and R²⁷, as defined below; and R′ is preferably Hor a polar or polarising group as defined below. On completion of thecoupling reaction, the halogen and boronic ester end groups arepreferably substituted by other groups, for example by hydrogenationand/or hydrolysis respectively.

Following the polymerization step to form the copolymer of the presentinvention, the copolymer may be cross-linked. Cross-linking may beachieved by any known technique.

Examples include the application of heat and/or moisture, ethylene oxidetreatment, UV irradiation, gamma sterilisation, electron beamirradiation, and autoclaving.

Thus, according to another aspect of the present invention, there isprovided a process for producing a Polycyclic Aromatic HydrocarbonCopolymer (PAHC) comprising copolymerising a composition containing atleast one polyacene monomer unit selected from the structure A′:

and at least one monomer unit selected from the structure B′:

wherein each of R groups, and k and 1 have the same general andpreferred meanings as described in relation to the PAHC definitionsabove; wherein Ar₁, Ar₂ and Ar₃, which may be the same or different,each represent an optionally substituted C₆₋₄₀ aromatic group(mononuclear or polynuclear), wherein preferably at least one of Ar₁,Ar₂ and Ar₃ is substituted with at least one polar or more polarisinggroup;wherein X′ is a halogen atom or a cyclic borate group; andwherein Y′ is a halogen atom.

Alternatively Y′ is a cyclic borate group and in this case X′ is ahalogen atom.

Preferably, the cyclic borate group is

Preferably, the process is carried out in a solvent, preferably anorganic solvent, preferably an aromatic organic solvent.

The compositions of the present invention can comprise additionalcurable monomers, for example, diluent monomers. Examples of suitablematerials include radically curable monomer compounds, such as acrylateand methacrylate monomer compounds. Examples of acrylate andmethacrylate monomers include isobornyl acrylate, isobornylmethacrylate, lauryl acrylate, lauryl methacrylate, isodecylacrylate,isodecylmethacrylate, caprolactone acrylate, 2-phenoxyethyl acrylate,isooctylacrylate, isooctylmethacrylate, butyl acrylate, alkoxylatedlauryl acrylate, ethoxylated nonyl phenol acrylate, ethoxylated nonylphenol methacrylate, ethoxylated hydroxyethyl methacrylate, methoxypolyethylene glycol monoacrylate, methoxy polyethylene glycolmonomethacrylate, tetrahydrofurfuryl methacrylate, as well as mixturesor combinations thereof.

In addition, multifunctional acrylate and methacrylate monomers andoligomers can be included in the compositions as reactive diluents andas materials that can increase the crosslink density of the curedcomposition. Examples of suitable multifunctional acrylate andmethacrylate monomers and oligomers include pentaerythritoltetraacrylate, pentaerythritol tetramethacrylate, 1,2-ethylene glycoldiacrylate, 1,2-ethylene glycol dimethacrylate, 1,6-hexanedioldiacrylate, 1,6-hexanediol dimethacrylate, 1,12-dodecanol diacrylate,1,12-dodecanol dimethacrylate, tris(2-hydroxy ethyl) isocyanuratetriacrylate, propoxylated neopentyl glycol diacrylate, hexanedioldiacrylate, tripropylene glycol diacrylate, dipropylene glycoldiacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol Adimethacrylate, alkoxylated hexanediol diacrylate, alkoxylatedcyclohexane dimethanol diacrylate, polyethylene glycol diacrylate,polyethylene glycol dimethacrylate, tris (2-hydroxy ethyl) isocyanuratetriacrylate, amine modified polyether acrylates (available as PO 83 F®,LR 8869®, and/or LR 8889® (all available from BASF Corporation),trimethylolpropane triacrylate, glycerol propoxylate triacrylate,dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate,ethoxylated pentaerythritol tetraacrylate (available from Sartomer Co.Inc. as SR 494®), as well as mixtures and combinations thereof. When areactive diluent is added to the composition of the present invention,the reactive diluent is added in any desired or effective amount, in oneembodiment at least about 1 percent by weight of the carrier, at leastabout 35 percent by weight of the carrier, no more than about 98 percentby weight of the carrier, no more than about 75 percent by weight of thecarrier, although the amount of diluent can be outside of these ranges.

Copolymers according to the present invention may have a permittivity at1000 Hz of greater than 1.5, preferably greater than 2, preferablygreater than 3. Particularly preferably, copolymers according to thepresent invention are semiconducting copolymers having a permittivity at1000 Hz of between 1.5 and 8, more preferably between 3.4 and 8. In apreferred embodiment, the polyacene copolymers have a permittivity at1000 Hz of between 3.4 and 7, more preferably between 3.4 and 6.5, yetmore preferably between 3.4 and 4.5 and even more preferably between 3.4and 4.0. Copolymers according to the present invention are preferablysemiconducting copolymers and may have a permittivity at 1000 Hz ofgreater than 3.4, for example greater than 3.8, greater than 4.0,greater than 4.2 and the like.

Preferably, the organic semiconductor compositions according to thepresent invention contain less than 10% by weight, more preferably lessthan 5% by weight, more preferably less than 1% by weight, morepreferably, substantially no copolymers which have a permittivity at1000 Hz of less than 3.4. In a preferred embodiment, the permittivity isdetermined by the method disclosed in WO 2004/102690 or by using themethod disclosed herein, preferably by using the method disclosedherein.

Preferably, the copolymers of the present invention are semiconductingcopolymers having a permittivity at 1000 Hz of between 3.4 and 8. In apreferred embodiment, the copolymers have a permittivity at 1000 Hz ofbetween 3.4 and 7, more preferably between 3.4 and 6.5, and even morepreferably between 3.4 and 4.5. The permittivity of the copolymers canbe measured using any standard method known to those skilled in the art.In a preferred embodiment, the permittivity is determined by the methoddisclosed in WO 2004/102690 or by using the method disclosed herein,preferably by using the method disclosed herein.

Monomer Units of Formula (A)

The following are some preferred characteristics of the polyacenemonomer units defined above as (A).

In a preferred embodiment, at least one (and more preferably 2) ofgroups R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³ and R¹⁴are tri-C₁₋₂₀ hydrocarbylsilyl C₁₋₄ alkynyl groups.

Preferably at least one (and more preferably 2) of groups R¹, R², R³,R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³ and R¹⁴ aretrihydrocarbylsilyl ethynyl groups.

In a preferred embodiment, at least one (and more preferably 2) ofgroups R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³ and R¹⁴are (trihydrocarbylsilyl)ethynyl- groups, —C≡C—SiR²²R²³R²⁴, wherein R²²,R²³ and R²⁴ independently represent C₁-C₆ alkyl or C₂-C₆ alkenyl. In amore preferred embodiment, R²², R²³ and R²⁴ are independently selectedfrom the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl, t-butyl, 1-propenyl and 2-propenyl.

In a preferred embodiment, R⁶ and R¹³ are trialkylsilyl ethynyl groups,—C≡C—SiR²²R²³R²⁴, wherein R²², R²³ and R²⁴ independently represent C₁-C₆alkyl or C₂-C₆ alkenyl. In a more preferred embodiment, R²², R²³ and R²⁴are independently selected from the group consisting of methyl, ethyl,propyl, isopropyl, n-butyl, isobutyl, t-butyl 1-propenyl and 2-propenyl.

In yet another preferred embodiment, when k=1=1; R¹, R², R³, R⁴, R⁸, R⁹,R¹⁰ and R¹¹ independently represent H, C₁-C₆ alkyl or C₁-C₆ alkoxy. Morepreferably, R¹, R⁴, R⁸ and R¹¹ are the same and represent H, C₁-C₆ alkylor C₁-C₆ alkoxy. In an even more preferred embodiment, R¹, R², R³, R⁴,R⁸, R⁹, R¹⁰ and R¹¹ are the same or different and are selected from thegroup consisting of hydrogen, methyl, ethyl, propyl, n-butyl, isobutyl,t-butyl, methoxy, ethoxy, propyloxy and butyloxy.

Preferably, R⁵, R⁷, R¹² and R¹⁴ are hydrogen.

Preferably, R²², R²³ and R²⁴ are independently selected from the groupconsisting hydrogen, a C₁-C₁₀ alkyl group (preferably C₁-C₄-alkyl andmost preferably methyl, ethyl, n-propyl or isopropyl) which mayoptionally be substituted for example with a halogen atom.

R²² and R²³ are preferably independently selected from the groupconsisting optionally substituted C₁₋₁₀ alkyl group and optionallysubstituted C₂₋₁₀ alkenyl, more preferably C₁-C₆ alkyl or C₂-C₆ alkenyl.A preferred alkyl group in this case is isopropyl.

Examples of the silyl group —Si(R²²)_(x)(R²³)_(y)(R²⁴)_(z) include,without limitation, trimethylsilyl, triethylsilyl, tripropylsilyl,dimethylethyl silyl, diethylmethylsilyl, dimethylpropylsilyl,dimethylisopropylsilyl, dipropylmethylsilyl, diisopropylmethylsilyl,dipropylethylsilyl, diisopropylethylsilyl, diethylisopropylsilyl,triisopropylsilyl, trimethoxysilyl, triethoxysilyl, triphenylsilyl,diphenylisopropylsilyl, diisopropylphenylsilyl, diphenylethyl silyl,diethylphenylsilyl, diphenylmethylsilyl, triphenoxysilyl,dimethylmethoxysilyl, dimethylphenoxysilyl, methylmethoxyphenyl, etc.For each example in the foregoing list, the alkyl, aryl or alkoxy groupmay optionally be substituted.

In a preferred embodiment of the first aspect of the invention, PAHCsaccording to the present invention comprise at least one monomer unithaving the Formula (A1):

wherein each of R⁵, R⁷, R¹² and R¹⁴ are hydrogen; R⁶ and R¹³ aretrialkylsilyl ethynyl groups, —C≡C—SiR²²R²³R²⁴, wherein R²², R²³ and R²⁴independently represent C₁-C₄ alkyl or C₂-C₄ alkenyl;

R¹, R², R³, R⁴, R⁸, R⁹, R¹⁰ and R¹¹ are independently selected from thegroup consisting of hydrogen; a branched or unbranched, unsubstitutedC₁-C₄ alkyl group; C₁-C₆ alkoxy group and C₆-C₁₂ aryloxy group;

Provided that at least one of each pair of R²/R³ and R⁹/R¹⁰ are a bond,represented by

, to another monomer unit having the Formula (A), (A1) or (B) and

wherein k and 1 are independently 0, or 1, preferably both k and 1 are1.

In monomer units of Formula (A1), wherein k and 1 are both 1; R⁶ and R¹³are (trialkylsilyl)ethynyl groups, —C≡C—SiR²²R²³R²⁴, wherein R²², R²³and R²⁴ are preferably selected from ethyl, n-propyl, isopropyl,1-propenyl or 2-propenyl; R¹, R², R³, R⁴, R⁸, R⁹, R¹⁰ and R¹¹ areindependently selected from the group consisting of hydrogen, methyl,ethyl and methoxy, provided that at least one of each pair of R²/R³ andR⁹/R¹⁰ are a bond, represented by

, to another monomer unit having the Formula (A), (A1) or (B).

In a more preferred embodiment the polyacene moiety in the PAHCcopolymer is a substituted pentacene, wherein each R²² group isindependently selected from the group consisting of a branched orunbranched, substituted or unsubstituted C₁-C₈ alkyl group, asubstituted or unsubstituted C₂-C₁₂ cycloalkyl group, and a substitutedor unsubstituted C₆-C₁₂ cycloalkylalkylene group; each R²³ group isindependently selected from the group consisting of a substituted orunsubstituted C₂-C₈ alkenyl group, a substituted or unsubstituted C₂-C₁₂cycloalkyl group, and a substituted or unsubstituted C₆-C₁₂cycloalkylalkylene group; and R²⁴ is independently selected from thegroup consisting of hydrogen, a branched or unbranched, substituted orunsubstituted C₂-C₈ alkynyl group, a substituted or unsubstituted C₂-C₁₂cycloalkyl group, a substituted or unsubstituted C₆-C₁₂cycloalkylalkylene group, a substituted C₅-C₁₂ aryl group, a substitutedor unsubstituted C₆-C₁₄ arylalkylene group, an acetyl group, asubstituted or unsubstituted C₅-C₁₂ heterocyclic ring comprising atleast one of O, N, S and Se in the ring.

Preferred PAHCs and compositions of the present invention contain atleast 20 wt. % (of the total of all monomer units (A), (A1) and (B), inthe copolymer or composition) of a polyacene monomer unit having theFormula (A1) and at least 20 wt. %, preferably between 20-80 wt. % of amonomer unit having the Formula (B).

Especially preferred polyacene monomer units according to the presentinvention are those of Formulae (A2)

wherein R¹, R⁴, R⁸ and R¹¹ are independently selected from the groupconsisting of H, C₁-C₆ alkyl and C₁-C₆ alkoxy.

Preferably R¹, R⁴, R⁸ and R¹¹ are the same or different and areindependently selected from the group consisting of hydrogen, methyl,ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxyand butyloxy, more preferably hydrogen, methyl, propyl and methoxy.

In monomer units of Formula (A2), R², R³, R⁹ and R¹⁰ are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₁-C₆ alkoxy,provided that at least one of each pair of R²/R³ and R⁹/R¹⁰ are a bond,represented by

, to another monomer unit having the Formula (A), (A1), (A2) or (B). Ina preferred embodiment, R², R³, R⁹ and R¹⁰ are the same or different andare independently selected from the group consisting of hydrogen,methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy,propyloxy and butyloxy, more preferably hydrogen, methyl, ethyl, propyland methoxy, provided that at least one of each pair of R²/R³ and R⁹/R¹⁰are a bond, represented by

, to another monomer unit having the Formula (A), (A1), (A2), or (B).

In monomer units of Formulae (A2), R²⁵, R²⁶ and R²⁷ are independentlyselected from the group consisting of C₁-C₆ alkyl and C₂-C₆ alkenyl,preferably R²⁵, R²⁶ and R²⁷ are independently selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,t-butyl, 1-propenyl and 2-propenyl, more preferably ethyl, n-propyl andisopropyl.

Preferred PAHCs and compositions of the present invention contain atleast 20 wt. % (of the total of all monomer units in the copolymer orcomposition) of a polyacene monomer unit having the Formula (A2) and atleast 20 wt. %, preferably between 20-80 wt. % of a monomer unit havingthe Formula (B).

In yet another preferred embodiment, the polyacene monomer units of thepresent invention are those of Formulae (A3) and (A4):

wherein R²⁵, R²⁶ and R²⁷ are independently selected from the groupconsisting of methyl, ethyl and isopropyl;wherein R¹, R², R³, R⁴, R⁸, R⁹, R¹⁰ and R¹¹ are independently selectedfrom the group consisting of C₁-C₆ alkyl, C₁-C₆ alkoxy and C₆-C₂₀aryloxy. Preferably R¹, R², R³, R⁴, R⁸, R⁹, R¹⁰ and R¹¹ areindependently selected from the group consisting of methyl, ethyl,propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxy andbutyloxy groups, wherein

represents a bond to another monomer unit having the Formula (A), (A1),(A2), (A3), (A4) or (B).

In some preferred embodiments, when R¹, R⁴, R⁸ and R¹¹ are the same andare methyl or methoxy groups, R²⁵, R²⁶ and R²⁷ are the same and areethyl or isopropyl groups. In a preferred embodiment, when R¹, R⁴, R⁸and R¹¹ are methyl groups, R²⁵, R²⁶ and R²⁷ are ethyl groups. In yetanother a preferred embodiment, when R¹, R⁴, R⁸ and R¹¹ are methylgroups, R²⁵, R²⁶ and R²⁷ are isopropyl groups. In a further preferredembodiment, when R¹, R⁴, R⁸ and R¹¹ are methoxy groups, R²⁵, R²⁶ and R²⁷are ethyl groups. In yet another preferred embodiment, when R¹, R⁴, R⁸and R¹¹ are methoxy groups, R²⁵, R²⁶ and R²⁷ are isopropyl groups.

In some preferred embodiments when R², R³, R⁹ and R¹⁰ are the same andare methyl or methoxy groups, R²⁵, R²⁶ and R²⁷ are the same and areethyl or isopropyl groups. In a preferred embodiment, when R², R³, R⁹and R¹⁰ are methyl groups, R²⁵, R²⁶ and R²⁷ are ethyl groups. In yetanother a preferred embodiment, when R², R³, R⁹ and R¹⁰ are methylgroups, R²⁵, R²⁶ and R²⁷ are isopropyl groups. In a further preferredembodiment, when R², R³, R⁹ and R¹⁰ are methoxy groups, R²⁵, R²⁶ and R²⁷are ethyl groups. In yet another preferred embodiment, when R², R³, R⁹and R¹⁰ are methoxy groups, R²⁵, R²⁶ and R²⁷ are isopropyl groups.

In an even more preferred embodiment of the present invention, thepolyacene monomer unit is selected from the following units (A5) to(A8):

Preferred PAHCs and compositions of the present invention contain atleast 20 wt. % (of the total of all monomer units (A) and (B) in thecopolymer or composition) of a polyacene monomer unit having the Formula(A3), (A4), (A5), (A6), (A7) or (A8) and at least 20 wt. %, preferablybetween 20-80 wt. % of a monomer unit having the Formula (B).

The “R” substituents (that is R¹, R², etc) denote the substituents atthe positions of pentacene according to conventional nomenclature:

Polyacene monomers according to the present invention may be synthesisedby any known method within the common general knowledge of a personskilled in the art. In a preferred embodiment, methods disclosed in US2003/0116755 A, U.S. Pat. No. 3,557,233, U.S. Pat. No. 6,690,029 WO2007/078993, WO 2008/128618 and Organic Letters, 2004, Volume 6, number10, pages 1609-1612 can be employed for the synthesis of polyacenecompounds used in the present invention. High permittivity analogues ofthe PAHCs of the invention may be prepared according to WO2012/160383and WO2012/164282.

Monomer Units (B)

The following are some preferred characteristics of the triarylaminemonomer unit defined above as (B),

Preferably, in monomer unit (B), Ar₁, Ar₂ and Ar₃, which may be the sameor different, each represent, independently if in different repeatunits, an optionally substituted C₆₋₂₀ aromatic group (mononuclear orpolynuclear), wherein at least one of Ar₁, Ar₂ and Ar₃ is substitutedwith at least one polar or more polarising group, and n=1 to 100,preferably 1 to 50, preferably 1 to 20, even more preferably 1 to 10 andmore preferably 1 to 5, wherein n refers to the number of monomer units.Preferably, at least one of Ar₁, Ar₂ and Ar₃ is substituted with 1, 2,3, or 4, more preferably 1, 2 or 3, more preferably 1 or 2, preferably 1polar or more polarising group(s).

In a preferred embodiment, the one or more polar or polarising group(s)is independently selected from the group consisting of nitro group,nitrile group, C₁₋₄₀ alkyl group substituted with a nitro group, anitrile group, a cyanate group, an isocyanate group, a thiocyanate groupor a thioisocyanate group; C₁₋₄₀ alkoxy group optionally substitutedwith a nitro group, a nitrile group, a cyanate group, an isocyanategroup, a thiocyanate group or a thioisocyanate group; C₁₋₄₀ carboxylicacid group optionally substituted with a nitro group, a nitrile group, acyanate group, an isocyanate group, a thiocyanate group or athioisocyanate group; C₂₋₄₀ carboxylic acid ester optionally substitutedwith a nitro group, a nitrile group, a cyanate group, an isocyanategroup, a thiocyanate group or a thioisocyanate group; sulfonic acidoptionally substituted with a nitro group, a nitrile group, a cyanategroup, an isocyanate group, a thiocyanate group or a thioisocyanategroup; sulfonic acid ester optionally substituted with a nitro group, anitrile group, a cyanate group, an isocyanate group, a thiocyanate groupor a thioisocyanate group; cyanate group, isocyanate group, thiocyanategroup, thioisocyanate group; and an amino group optionally substitutedwith a nitro group, a nitrile group, a cyanate group, an isocyanategroup, a thiocyanate group or a thioisocyanate group; and combinationsthereof.

In a more preferred embodiment, the one or more polar or polarisinggroup(s) is independently selected from the group consisting of nitrogroup, nitrile group, C₁₋₁₀ alkyl group substituted with a nitrilegroup, a cyanate group, or an isocyanate group; C₁₋₂₀ alkoxy group,C₁₋₂₀ carboxylic acid group, C₂₋₂₀ carboxylic acid ester; sulfonic acidester; cyanate group, isocyanate group, thiocyanate group,thioisocyanate group, and an amino group; and combinations thereof.

More preferably the polar or polarizing group is selected from the groupconsisting of C₁₋₄ cyanoalkyl group, C₁₋₁₀ alkoxy group, nitrile groupand combinations thereof.

More preferably the polar or polarizing group(s) is selected from thegroup consisting of cyanomethyl, cyanoethyl, cyanopropyl, cyanobutyl,methoxy, ethoxy, propoxy, butoxy, nitrile, NH₂ and combinations thereof.Preferably at least one of Ar₁, Ar₂ and Ar₃ is substituted with 1 or 2polar or more polarising group, which may be the same or different.

Yet more preferably, polar or polarizing group(s) is selected from thegroup consisting of isopropyl cyano, cyclohexylcyano, methoxy, ethoxy,nitrile and combinations thereof. Preferably at least one of Ar₁, Ar₂and Ar₃ is substituted with 1 or 2 polar or more polarising group, whichmay be the same or different.

More preferably, polar or polarizing group(s) is selected from the groupconsisting of methoxy, ethoxy, propoxy, butoxy and combinations thereof,wherein at least one of Ar₁, Ar₂ and Ar₃ is substituted with 1 or 2polar or more polarising group, which may be the same or different.

More preferably, polar or polarizing group(s) is selected from the groupconsisting of methoxy and ethoxy, wherein at least one of Ar₁, Ar₂ andAr₃ is substituted with 1 or 2 of the same polar or more polarisinggroup.

In the context of Ar₁, Ar₂ and Ar₃, a mononuclear aromatic group hasonly one aromatic ring, for example phenyl or phenylene. A polynucleararomatic group has two or more aromatic rings which may be fused (forexample napthyl or naphthylene), individually covalently linked (forexample biphenyl) and/or a combination of both fused and individuallylinked aromatic rings. Preferably each Ar₁, Ar₂ and Ar₃ is an aromaticgroup which is substantially conjugated over substantially the wholegroup.

Preferably, Ar₁, Ar₂ and Ar₃, are independently selected from the groupconsisting of C₆₋₂₀ aryl, C₇₋₂₀ aralkyl and C₇₋₂₀ alkaryl, any of whichmay be substituted with 1, 2, or 3 groups independently selected fromC₁₋₄ alkoxy, C₃₋₂₀ cycloalkylcyano, C₁₋₄ cyanoalkyl, CN and mixturesthereof, and n=1 to 10, wherein n refers to the number of monomer units.

Preferably, Ar₁, Ar₂ and Ar₃, are independently selected from the groupconsisting of C₆₋₁₀ aryl, C₇₋₁₂ aralkyl and C₇₋₁₂ alkaryl, any of whichmay be substituted with 1, 2, or 3 groups independently selected fromC₁₋₂ alkoxy, C₁₋₃ cyanoalkyl, CN and mixtures thereof, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are independently selected from the groupconsisting of C₆₋₂₀ aryl, substituted with 1 or 2 groups independentlyselected from C₁₋₄ alkoxy, C₃₋₂₀ cycloalkylcyano, C₁₋₄ cyanoalkyl, CNand mixtures thereof, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are independently selected from the groupconsisting of C₆₋₁₀ aryl, wherein Ar₃, is substituted with 1 or 2 C₁₋₄alkoxy, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are independently selected from the groupconsisting of C₆₋₁₀ aryl, wherein Ar₃ is substituted with 1 C₁₋₄ alkoxy,and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are independently selected from the groupconsisting of phenyl, benzyl, tolyl and naphthyl, any of which may besubstituted with 1, 2 or 3 groups independently selected from methoxy,ethoxy, cyanomethyl, cyanoethyl, CN and mixtures thereof, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are all phenyl, wherein Ar₃ is substitutedwith 1 or 2 C₁₋₄ alkoxy, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are all phenyl which may be independentlysubstituted with 1, 2 or 3 groups selected from methoxy, ethoxy,isoprorylcyano, cyanomethyl, cyanoethyl, CN and mixtures thereof, andn=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are all phenyl which may be independentlysubstituted with 1 or 2 groups selected from methoxy, ethoxy,cyanomethyl, CN and mixtures thereof, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are all phenyl which may be independentlysubstituted with 1 or 2 groups selected from methoxy, ethoxy andmixtures thereof, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are all phenyl which may be independentlysubstituted with 2,4-dimethoxy, 2-cyano, 2-methoxy, 2-ethoxy, 4-methoxy,4-ethoxy, 4-isopropylcyano and 4-cyclohexylcyano, and n=1 to 10.

Preferably, Ar₁, Ar₂ and Ar₃, are all phenyl which may be independentlysubstituted with 2,4-dimethoxy, 2-methoxy, 2-ethoxy, 4-methoxy and4-ethoxy, and n=1 to 10.

The copolymers of the present invention may be a random or blockcopolymer of different monomer units. In such a case, any monomer unitdefined by Formula (A) or (B), may be combined with a different or samemonomer unit of (A) or (B) provided that at least one monomer unit (A)is bonded to at least one monomer unit (B).

The ratio of the monomers in the polycyclic aromatic hydrocarboncopolymers can be altered to allow for adjustment of the permittivityrelative to a homopolymer. Furthermore, preferably the monomer unit of(A) or (B) may be mixed with monomer units which do not meet thedefinition of (A) or (B), provided that the average permittivity of thebinder in the compositions is preferably between 3.4 and 8.0. In thisregard, other suitable monomer units include fluorene monomers such as(C), indenofluorene monomers such as (D and D′) and sprirobifluorenemonomers such as (E): wherein each R^(1′), R^(2′), R^(3′), R^(4′),R^(5′), R^(6′) and R^(7′), each of which may be the same or different,is selected from the same group as R¹, R², R³, R⁴, R⁵, R⁶ and R⁷,already defined above.

n′=1 to 3.

When the PAHC according to the present invention comprises one or moremonomers (C), (D), (D′) and/or (E), the PAHC is comprised of monomer (A)in an amount of at least 20 wt. %; monomer (B) in an amount of at least60 wt. % and the remainder is comprised of monomers (C), (D), (D′)and/or (E), based on the total weight of all monomer units in thecopolymer.

In an even more preferred embodiment of the present invention, themonomer unit (B) comprises at least one unit having the structures (F)to (J):

Organic Semiconductor Compositions

An organic semiconductor composition according to the first aspect ofthe present invention comprises a copolymer composition, the compositionhaving a permittivity at 1000 Hz of greater than 1.5, more preferablygreater than 3.4, and yet more preferably between 1.5 and 6.5, even morepreferably between 3 and 6.5, more preferably between 3.0 to 5.0 andstill more preferably between 3.4 to 4.5.

The organic semiconductor composition according to the present inventioncan comprise a polycyclic aromatic hydrocarbon copolymer as hereindisclosed. In a preferred embodiment, an organic semiconductorcomposition may comprise a copolymer as defined herein, furthercomprising a polycrystalline polyacene small molecule semiconductor asdescribed in our application WO 2012/164282, wherein the PAHC has apermittivity at 1000 Hz of between 3.4 and 8, preferably between 3.4 and6.5, more preferably between 4 and 6.5, yet more preferably between 3.4to 4.5. In a preferred embodiment, a copolymer as defined herein may beused in combination with a polyacene small molecule, where the ‘driedstate’ composition contains between 10 to 50% of the polyacene smallmolecule and 10 to 90% of the PAHC.

The organic semiconductor composition according to the present inventioncan comprise a polycyclic aromatic hydrocarbon copolymer as hereindisclosed. In a preferred embodiment, an organic semiconductorcomposition may comprise a copolymer as defined herein, furthercomprising an organic binder, wherein the organic binder has apermittivity at 1000 Hz of between 3.4 and 8, preferably between 3.4 and6.5, more preferably between 4 and 6.5, yet more preferably between 3.4to 4.5.

In a particularly preferred embodiment, a copolymer as defined hereinmay be used in combination with an organic binder, wherein the organicbinder has a permittivity at 1000 Hz of between 3.4 and 8.0, preferablybetween 3.6 and 6.5, more preferably between 3.4 to 4.5.

In yet another preferred embodiment, a copolymer of the inventionpreferably has a permittivity at 1000 Hz of between 3.4 and 8.0,preferably between 3.4 and 4.5.

The concentration of the copolymer and solvent present in thecomposition will vary depending on the preferred solution coatingmethod, for example ink jet printing compositions require low viscosity,low solids loading compositions, whilst screen printing processesrequire high viscosity, high solids loading compositions. Followingdeposition of the copolymer composition, the solvent is preferablyevaporated to afford the semiconductor layer having 1-99.9% by weight ofthe binder and 0.1 to 99% by weight of the copolymer (in the printed ordried state) based on a total weight of the composition; preferably thesemiconductor layer having 25 to 75% by weight of the small moleculepolyacene and 25 to 75% by weight of the copolymer.

In the composition prior to deposition, one or more of theabove-described PAHCs is preferably present at a concentration of atleast 0.1 wt %, preferably 0.5 wt % based on a total weight of thecomposition. The upper limit of the concentration of the PAHC in thecomposition is often near the solubility limit of that copolymer in theparticular solvent at the temperature of the composition during itsapplication to a substrate such as in the fabrication of an electronicdevice. Typical compositions of the present invention comprise one ofthe PAHCs at a concentration ranging from about 0.1 wt %, preferably 0.5wt % to about 20.0 wt % based on a total weight of the composition, moretypically, from about 0.5 wt % to about 10.0 wt %, more typically 0.5 to5.0, more typically 1 to 3 wt %.

In the printed or dried composition, one or more of the above-describedPAHcs is preferably present at a concentration of at least 10 wt % basedon a total weight of the composition, preferably between 10 and 90 wt %,more preferably between 20 and 80 wt %, more preferably between 30 and70 wt %, more preferably between 40 and 60 wt %.

In a preferred embodiment, one or more solvents may be present in theorganic semiconductor compositions.

Suitable solvents include, but are not limited to, tetrahydrofuran,aromatic hydrocarbons such as toluene, o-xylene, m-xylene, p-xylene,mesitylene, bromomesitylene, anisole, bromoanisole, bromobenzene,tetralin, o-xylene, 1,4-dioxane, methylethylketone, gamma-butyrolactone,cyclohexanone, morpholine, N-methylpyrollidone, ethyl acetate, n-butylacetate, dimethylformamide, dimethylacetamide, decalin or mixtures oftwo or more thereof. Preferably, no chlorinated solvents are used.

Solvent blends may also be utilised. Suitable solvent blends include,but are not limited to compositions of the above solvents in conjunctionwith solvents such as dimethylformamide, dimethylacetamide,dimethylsulfoxide, methyl ethyl ketone, dichloromethane,dichlorobenzene, furfuryl alcohol, dimethoxyethane and ethyl acetate,higher boiling point alkanes such as n-heptane and alcohols such asisopropyl alcohol. Such compositions (prior to deposition) preferablycontain a suitable solvent in an amount of greater than 50 wt % based ona total weight of the composition, preferably between 60 and 95 wt %based on a total weight of the composition.

In yet another preferred embodiment, one or more additional compositioncomponents may be present in the organic semiconductor composition.Suitable additional composition components include, but are not limitedto, a polymer additive, a rheological modifier, a surfactant, anothersemiconductor that is a matched hole transfer compound for thecopolymer. In some exemplary embodiments, the compositions comprise apolymer additive selected from the group consisting of polystyrene,poly(alpha-methylstyrene), poly(pentafluorostyrene), poly(methylmethacrylate), poly(4-cyanomethyl styrene), poly(4-vinylphenol), or anyother suitable polymer disclosed in U.S. Patent Application PublicationNo. 2004/0222412 A1 or U.S. Patent Application Publication No.2007/0146426 A1. In some desired embodiments, the polymer additivecomprises polystyrene, poly(alpha-methylstyrene),poly(pentafluorostyrene) or poly(methyl methacrylate). In some exemplaryembodiments, the compositions comprise a surfactant selected fromfluorinated surfactants or fluorosurfactants. When present, eachadditional composition component is independently present in an amountof greater than 0 to about 50 wt % based on a total weight of thecomposition. Preferably, each additional composition component isindependently present in an amount ranging from about 0.0001 to about10.0 wt % based on a total weight of the composition. For example, whena polymer is present in the composition, the polymer additive istypically present in an amount of greater than 0 to about 5.0 wt %,preferably from about 0.5 to about 3.0 wt % based on a total weight ofthe composition. For example, when a surfactant is present in thecomposition, the surfactant is preferably present in an amount ofgreater than 0 to about 1.0 wt %, more typically, from about 0.001 toabout 0.5 wt % based on a total weight of the composition.

The organic semiconductor composition according to the present inventionpreferably has a charge mobility value of at least 0.5 cm²V⁻¹s⁻¹,preferably between 0.5 and 8.0 cm²V⁻¹s⁻¹, more preferably between 0.5and 6.0 cm²V⁻¹s⁻¹, more preferably between 0.8 and 5.0 cm²V⁻¹s⁻¹, morepreferably between 1.0 and 5.0 cm²V⁻¹s⁻¹, more preferably between 1.5and 5.0 cm²V⁻¹s⁻¹, more preferably between 2.0 and 5.0 cm²V⁻¹s⁻¹. Thecharge mobility value of the semiconductor composition can be measuredusing any standard method known to those skilled in the art, such astechniques disclosed in J. Appl. Phys., 1994, Volume 75, page 7954 andWO 2005/055248, preferably by those described in WO 2005/055248.

The organic semiconductor composition according to the present inventionmay be prepared by any known method within the common general knowledgeof a person skilled in the art. In a preferred embodiment, the organicsemiconductor composition is prepared by the method disclosed in WO2005/055248 or by using the method disclosed herein, preferably by usingthe method disclosed herein.

Preferably, organic semiconductor compositions according to the presentinvention are semiconducting compositions having a permittivity at 1000Hz greater than 1.5, more preferably greater than 3.4, and yet morepreferably, between 3.4 and 8. In a preferred embodiment, thecompositions have a permittivity at 1000 Hz of between 4.0 and 7, morepreferably between 4.0 and 6.5, even more preferably between 4.0 and 6and yet more preferably between 3.4 and 4.5.

Organic Semiconductor Layers

The organic semiconductor compositions according to the presentinvention may be deposited onto a variety of substrates, to form organicsemiconductor layers.

The organic semiconductor layer according to the present invention maybe prepared using a method comprising the steps of:

-   -   (i) Mixing the organic semiconductor composition according to        the present invention with a solvent to form a semiconductor        layer formulation;    -   (ii) Depositing said formulation onto a substrate; and    -   (iii) Optionally removing the solvent to form an organic        semiconductor layer.

Useful substrate materials include, but are not limited to, polymericfilms such as polyamides, polycarbonates, polyimides, polyketones,polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), andinorganic substrates such as silica, alumina, silicon wafers and glass.The surface of a given substrate may be treated, e.g. by reaction ofchemical functionality inherent to the surface with chemical reagentssuch as silanes or exposure of the surface to plasma, in order to alterthe surface characteristics.

Prior to depositing the organic semiconductor composition onto thesubstrate, the composition may be combined with one or more solvents inorder to facilitate the deposition step. Suitable solvents include anysolvent which is able to dissolve both the copolymer, and which uponevaporation from the solution blend, give a coherent, defect-free layer.Suitable solvents for the copolymer can be determined by preparing acontour diagram for the material as described in ASTM Method D 3132 atthe concentration at which the mixture will be employed. The material isadded to a wide variety of solvents as described in the ASTM method.

Suitable solvents include, but are not limited to, tetrahydrofuran,aromatic hydrocarbons such as toluene, o-xylene, m-xylene, p-xylene,mesitylene, bromomesitylene, anisole, bromoanisole, bromobenzene,tetralin, o-xylene, 1,4-dioxane, methylethylketone, gamma-butyrolactone,cyclohexanone, morpholine, N-methylpyrollidone, ethyl acetate, n-butylacetate, dimethylformamide, dimethylacetamide, decalin or mixtures oftwo or more thereof. Preferably, no chlorinated solvents are used.

In accordance with the present invention it has further been found thatthe level of the solids content in the organic semiconducting layerformulation is also a factor in achieving improved mobility values forelectronic devices such as OFETs. The solids content of the formulationis commonly expressed as follows:

${{Solids}\mspace{14mu} {content}\mspace{14mu} (\%)} = {\frac{a + b}{a + b + c} \times 100}$

wherein: a=mass of polyacene small molecule, b=mass of PAHC and c=massof solvent.

The solids content of the formulation is preferably 0.1 to 10% byweight, more preferably 0.5 to 5% by weight.

Suitable conventional deposition methods include, but are not limitedto, spin coating, spray coating, blade/slot-die coating, flexographicprinting, gravure printing, roll-to-roll web-coating, and dip coating,as well as printing processes such as ink-jet printing, screen printing,and offset lithography. In one desired embodiment, the resultingcomposition is a printable composition, even more desirably, an ink jetprintable composition.

Once the composition is deposited onto a substrate surface, the solventmay be removed to form an organic semiconductor layer. Any suitablemethod may be used to remove the solvent. For example, the solvent maybe removed by evaporation or drying. Typically, at least about 80percent of the solvent is removed to form the semiconductor layer. Forexample, at least about 85 weight percent, at least about 90 weightpercent, at least about 92 weight percent, at least about 95 weightpercent, at least about 97 weight percent, at least about 98 weightpercent, at least about 99 weight percent, or at least about 99.5 weightpercent of the solvent is removed.

The solvent often can be evaporated at any suitable temperature. In somemethods, the solvent mixture is evaporated at ambient temperature. Inother methods, the solvent is evaporated at a temperature higher orlower than ambient temperature. For example, a platen supporting thesubstrate can be heated or cooled to a temperature higher or lower thanambient temperature. In still other preferred methods, some or most ofthe solvent can be evaporated at ambient temperature, and any remainingsolvent can be evaporated at a temperature higher than ambienttemperature. In methods where the solvent evaporates at a temperaturehigher than ambient temperature, the evaporation can be carried outunder an inert atmosphere, such as a nitrogen atmosphere.

Alternatively, the solvent can be removed by application of reducedpressure (i.e., at a pressure that is less than atmospheric pressure)such as through the use of a vacuum. During application of reducedpressure, the solvent can be removed at any suitable temperature such asthose described above.

The rate of removal of the solvent can affect the resultingsemiconductor layer. For example, if the removal process is too rapid,poor packing of the semiconductor molecules can occur duringcrystallisation. Poor packing of the semiconductor molecules can bedetrimental to the charge mobility of the semiconductor layer. Thesolvent can evaporate entirely on its own in an uncontrolled fashion(i.e., no time constraints), or the conditions can be controlled inorder to control the rate of evaporation. In order to minimise poorpacking, the solvent can be evaporated while slowing the evaporationrate by covering the deposited layer. Such conditions can lead to asemiconductor layer having a relatively high degree of crystallinity.

After removal of a desired amount of solvent to form the semiconductorlayer, the semiconductor layer can be annealed by exposure to heat orsolvent vapours, i.e., by thermal annealing or solvent annealing.

The organic semiconductor layer according to the present inventionpreferably has a charge mobility value of at least 0.5 cm²V⁻¹s⁻¹,preferably between 0.5 and 8.0 cm²V⁻¹s⁻¹, more preferably between 0.5and 6.0 cm²V⁻¹s⁻¹, more preferably between 0.8 and 5.0 cm²V⁻¹s⁻¹, morepreferably between 1 and 5.0 cm²V⁻¹s⁻¹, more preferably between 1.5 and5.0 cm²V⁻¹s⁻¹, more preferably between 2.0 and 5.0 cm²V⁻¹s⁻¹. The chargemobility value of the semiconductor layer can be measured using anystandard method known to those skilled in the art, such as techniquesdisclosed in J. Appl. Phys., 1994, Volume 75, page 7954 and WO2005/055248, preferably by those described in WO 2005/055248.

Preferably, the organic semiconductor layer(s) of the present inventionare semiconducting layers having a permittivity at 1000 Hz of between3.4 and 8. In a preferred embodiment, the layer(s) have a permittivityat 1000 Hz of between 4.0 and 7, more preferably between 4.0 and 6.5,yet more preferably between 4.0 and 6 and even more preferably between3.4 and 4.5

Electronic Devices

The invention additionally provides an electronic device comprising theorganic semiconductor composition according to the present invention.The composition may be used, for example, in the form of asemiconducting layer or film. Additionally, the invention preferablyprovides an electronic device comprising the organic semiconductor layeraccording to the present invention.

The thickness of the layer or film may be between 0.02 and 20 microns,0.2 and 20 microns, preferably between 0.05 and 10 microns, preferablybetween 0.5 and 10 microns, between 0.05 and 5 microns, even morepreferably between 0.5 and 5 microns, yet more preferably between 0.5and 2 microns, and more preferably between 0.02 and 1 microns.

The electronic device may include, without limitation, organic fieldeffect transistors (OFETS), organic light emitting diodes (OLEDS),photodetectors, organic photovoltaic (OPV) cells, sensors, lasers,memory elements and logic circuits.

Exemplary electronic devices of the present invention may be fabricatedby solution deposition of the above-described organic semiconductorcomposition onto a substrate.

DETAILED DESCRIPTION OF THE INVENTION

General

The term “about” in relation to a numerical value x means, for example,x±10%.

The word “substantially” does not exclude “completely” e.g. acomposition which is “substantially free” from Y may be completely freefrom Y. Where necessary, the word “substantially” may be omitted fromthe definition of the invention.

“Molecular weight” of a polymeric material (including monomeric ormacromeric materials), as used herein, refers to the number-averagemolecular weight unless otherwise specifically noted or unless testingconditions indicate otherwise.

A “polymer” means a material formed by polymerising and/or crosslinkingone or more monomers, macromers and/or oligomers and having two or morerepeat units.

As used herein, the term “alkyl” group refers to a straight or branchedsaturated monovalent hydrocarbon radical, having the number of carbonatoms as indicated. By way of non limiting example, suitable alkylgroups include, methyl, ethyl, propyl, n-butyl, t-butyl, isobutyl anddodecanyl.

As used herein, the term “alkoxy” group include without limitation,methoxy, ethoxy, 2-methoxyethoxy, t-butoxy, etc.

As used herein, the term “amino” group includes, without limitation,dimethylamino, methylamino, methylphenylamino, phenylamino, etc.

The term “carbyl” refers to any monovalent or multivalent organicradical moiety which comprises at least one carbon atom other withoutany non-carbon atoms (—C≡C), or optionally combined with at least onenon-carbon atoms such as N, O, S, P, SI, Se, As, Te or Ge (for examplecarbonyl etc.).

The term “hydrocarbon” group denotes a carbyl group that additionallycontains one or more H atoms and optionally contains one or more heteroatoms.

A carbyl or hydrocarbyl group comprising 3 or more carbon atoms may belinear, branched and/or cyclic, including spiro and/or fused rings.

Preferred carbyl or hydrocarbyl groups include alkyl, alkoxy,alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyloxy, each of which isoptionally substituted and has 1 to 40, preferably 1 to 18 carbon atoms,furthermore optionally substituted aryl, aryl derivative or aryloxyhaving 6 to 40, preferably 6 to 18 carbon atoms, furthermorealkylaryloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy andaryloxycarbonyloxy, each or which is optionally substituted and has 7 to40, more preferable 7 to 25 carbon atoms.

The carbyl or hydrocarbyl group may be saturated or unsaturated acyclicgroup, or a saturated or unsaturated cyclic group. Unsaturated acyclicor cyclic groups are preferred, especially alkenyl and alkynyl groups(especially ethynyl).

In the polyacenes of the present invention, the optional substituents onthe said C₁-C₄₀ carbyl or hydrocarbyl groups for R₁-R₁₄ etc. preferablyare selected from: silyl, sulpho, sulphonyl, formyl, amino, imino,nitrilo, mercapto, cyano, nitro, halo, C₁₋₄ alkyl, C₆₋₁₂ aryl, C₁₋₄alkoxy, hydroxy and/or all chemically possible combinations thereof.More preferable among these optional substituents are silyl and C₆₋₁₂aryl and most preferable is silyl.

“Substituted alkyl group” refers to an alkyl group having one or moresubstituents thereon, wherein each of the one or more substituentscomprises a monovalent moiety containing one or more atoms other thancarbon and hydrogen either alone (e.g., a halogen such as F) or incombination with carbon (e.g., a cyano group) and/or hydrogen atoms(e.g., a hydroxyl group or a carboxylic acid group).

“Alkenyl group” refers to a monovalent group that is a radical of analkene, which is a hydrocarbon with at least one carbon-carbon doublebond. The alkenyl can be linear, branched, cyclic, or combinationsthereof and typically contains 2 to 30 carbon atoms. In someembodiments, the alkenyl contains 2 to 20, 2 to 14, 2 to 10, 4 to 10, 4to 8, 2 to 8, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkenyl groupsinclude, but are not limited to, ethenyl, propenyl, and butenyl.

“Substituted alkenyl group” refers to an alkenyl group having (i) one ormore C—C double bonds, and (ii) one or more substituents thereon,wherein each of the one or more substituents comprises a monovalentmoiety containing one or more atoms other than carbon and hydrogeneither alone (e.g., a halogen such as F) or in combination with carbon(e.g., a cyano group) and/or hydrogen atoms (e.g., a hydroxyl group or acarboxylic acid group).

“Alkynyl group” refers to a monovalent group that is a radical of analkyne, a hydrocarbon with at least one carbon-carbon triple bond. Thealkynyl can be linear, branched, cyclic, or combinations thereof andtypically contains 2 to 30 carbon atoms. In some embodiments, thealkynyl contains 2 to 20, 2 to 14, 2 to 10, 4 to 10, 4 to 8, 2 to 8, 2to 6, or 2 to 4 carbon atoms. Exemplary alkynyl groups include, but arenot limited to, ethynyl, propynyl, and butynyl.

“Substituted alkynyl group” refers to an alkynyl group having (i) one ormore C—C triple bonds, and (ii) one or more substituents thereon,wherein each of the one or more substituents comprises a monovalentmoiety containing one or more atoms other than carbon and hydrogeneither alone (e.g., a halogen such as F) or in combination with carbon(e.g., a cyano group) and/or hydrogen atoms (e.g., a hydroxyl group or acarboxylic acid group or a silyl group).

“Cycloalkyl group” refers to a monovalent group that is a radical of aring structure consisting of 3 or more carbon atoms in the ringstructure (i.e., only carbon atoms in the ring structure and one of thecarbon atoms of the ring structure is the radical).

“Substituted cycloalkyl group” refers to a cycloalkyl group having oneor more substituents thereon, wherein each of the one or moresubstituents comprises a monovalent moiety containing one or more atoms(e.g., a halogen such as F, an alkyl group, a cyano group, a hydroxylgroup, or a carboxylic acid group).

“Cycloalkylalkylene group” refers to a monovalent group that is a ringstructure consisting of 3 or more carbon atoms in the ring structure(i.e., only carbon atoms in the ring), wherein the ring structure isattached to an acyclic alkyl group (typically, from 1 to 3 carbon atoms,more typically, 1 carbon atom) and one of the carbon atoms of theacyclic alkyl group is the radical. “Substituted cycloalkylalkylenegroup” refers to a cycloalkylalkylene group having one or moresubstituents thereon, wherein each of the one or more substituentscomprises a monovalent moiety containing one or more atoms (e.g., ahalogen such as F, an alkyl group, a cyano group, a hydroxyl group, or acarboxylic acid group).

“Aryl group” refers to a monovalent group that is a radical of anaromatic carbocyclic compound. The aryl can have one aromatic ring orcan include up to 5 carbocyclic ring structures that are connected to orfused to the aromatic ring. The other ring structures can be aromatic,non-aromatic, or combinations thereof. Examples of preferred aryl groupsinclude, but are not limited to, phenyl, 2-tolyl, 3-tolyl, 4-tolyl,biphenyl, 4-phenoxyphenyl, 4-fluorophenyl, 3-carbomethoxyphenyl,4-carbomethoxyphenyl, terphenyl, anthryl, naphthyl, acenaphthyl,anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perylenyl, andfluorenyl.

“Substituted aryl group” refers to an aryl group having one or moresubstituents on the ring structure, wherein each of the one or moresubstituents comprises a monovalent moiety containing one or more atoms(e.g., a halogen such as F, an alkyl group, a cyano group, a hydroxylgroup, or a carboxylic acid group).

“Arylalkylene group” refers to a monovalent group that is an aromaticring structure consisting of 6 to 10 carbon atoms in the ring structure(i.e., only carbon atoms in the ring structure), wherein the aromaticring structure is attached to an acyclic alkyl group having one or morecarbon atoms (typically, from 1 to 3 carbon atoms, more typically, 1carbon atom) and one of the carbons of the acyclic alkyl group is theradical.

“Substituted arylalkylene group” refers to an arylalkylene group havingone or more substituents thereon, wherein each of the one or moresubstituents comprises a monovalent moiety containing one or more atoms(e.g., a halogen such as F, an alkyl group, a cyano group, a hydroxylgroup, or a carboxylic acid group).

“Acetyl group” refers to a monovalent radical having the formula—C(O)CH₃.

“Heterocyclic ring” refers to a saturated, partially saturated, orunsaturated ring structure comprising at least one of O, N, S and Se inthe ring structure.

“Substituted heterocyclic ring” refers to a heterocyclic ring having oneor more substituents bonded to one or more members of the ringstructure, wherein each of the one or more substituents comprises amonovalent moiety containing one or more atoms (e.g., a halogen such asF, an alkyl group, a cyano group, a hydroxyl group, or a carboxylic acidgroup).

“Carbocyclic ring” refers to a saturated, partially saturated, orunsaturated ring structure comprising only carbon in the ring structure.

“Substituted carbocyclic ring” refers to a carbocyclic ring having oneor more substituents bonded to one or more members of the ringstructure, wherein each of the one or more substituents comprises amonovalent moiety containing one or more atoms (e.g., a halogen such asF, an alkyl group, a cyano group, a hydroxyl group, or a carboxylic acidgroup).

“Ether group” refers to a —R_(a)—O—R_(b) radical wherein R_(a) is abranched or unbranched alkylene, arylene, alkylarylene or arylalkylenehydrocarbon and R_(b) is a branched or unbranched alkyl, aryl, alkylarylor arylalkyl hydrocarbon.

“Substituted ether group” refers to an ether group having one or moresubstituents thereon, wherein each of the one or more substituentscomprises a monovalent moiety containing one or more atoms other thancarbon and hydrogen either alone (e.g., a halogen such as F) or incombination with carbon (e.g., a cyano group) and/or hydrogen atoms(e.g., a hydroxyl group or a carboxylic acid group).

Unless otherwise defined, a “substituent” or “optional substituent” ispreferably selected from the group consisting of halo (I, Br, Cl, F),CN, NO₂, NH₂, —COOH and OH.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representation of top contact/bottom gate Organic Thin FilmTransistor (OTFT)

FIG. 2 is a representation of bottom contact/bottom gate OTFT

FIG. 3 is a representation of top contact/top gate OTFT

FIG. 4 is a representation of bottom contact/top gate OTFT

Labels—A: Substrate; B: Gate electrode; C: Dielectric layer; D:Semiconductor layer; E: Source electrode; F: Gate electrode

FIG. 5: Transfer characteristic for TG 10 micron channel length and 500micron channel width OTFT using 1,4,8,11-tetramethylbis-triethysilylethynyl pentacene and PAHC (1) described as Formulation(1). Drain voltage is −2V.

FIG. 6: Transfer characteristic for TG 30 micron channel length, 500micron channel width OTFT using 1,4,8,11-tetramethylbis-triethysilylethynyl pentacene and PAHC (1) described as Formulation(1). Drain voltage is −2V.

FIG. 7: Transfer characteristic for TG 30 micron channel length, 500micron channel width OTFT using 1,4,8,11-tetramethylbis-triethysilylethynyl pentacene and PAHC (3) described as Formulation(3). Drain voltage is −2V.

EXAMPLES OF THE PRESENT INVENTION

The following examples of the present invention are merely exemplary andshould not be viewed as limiting the scope of the invention.

Measurement of the Capacitance of the Polymer Binder

The polymer binder was diluted with tetralin in order to lower itsviscosity and make it possible to obtain a film thickness of ˜1 micronwhen spin coated for the spin speed range 1000-2000 rpm. The polymerbinder solution was spin coated at 500 rpm for 10 seconds, followed by1500 rpm for 30 seconds, onto ITO coated and cleaned 1×1 inch glasssubstrates.

To clean the ITO coated substrates they were submerged in a 3% solutionof DECon 90 and put in an ultrasonic bath (water temperature>65° C.),washed with deionised water, submerged in deionised water and put in anultrasonic bath (water temperature>65° C.), washed a further time withdeionised water, submerged in isopropyl alcohol and then put in anultrasonic bath (water temperature>65° C.), and then spin dried.

After deposition of the polymer binder the substrate was annealed on ahotplate at 120° C. for 5 minutes.

The substrate was then covered with a capacitance shadow mask, and topelectrodes were deposited by evaporation of gold using a thermaldeposition method. In order to determine the exact thickness of thepolymer binder layer, the thickness was measured using a Dektak 3030profilometer (available from Veeco, Plainview N.Y.) at three differentpositions and averaged; these values were subsequently used to calculatethe dielectric constants of the polymer binders.

Capacitance measurements were then carried out using impedance analyserAgilent 43961A and a probe station. In order to improve the electricalcontact between the ITO back electrode and the external probe electrode,a conductive silver paste was applied. The sample being measured wasplaced in a metal box on the metal plate to ensure minimum influencefrom the external environment.

Before each set of measurements was obtained, the analyser wascalibrated using the 43961A Impedance Test Kit as a compensation routinewas carried out to account for internal capacitance of the analyser andtest fixture. The measurement calibration was carried out with open andshorted circuit; the dielectric constant was calculated using thefollowing equation:

C=∈×∈ _(o)×(A/d).

Wherein C is the capacitance (Farads), A is the area (m²), d is thecoating thickness (m), ∈ is the dielectric constant (permittivity), and∈_(o) is the permittivity of free space and is taken as 8.8854×10⁻¹²F/m.

As a reference sample, a polystyrene sample (Mw˜350,000) having athickness of 1 am was tested. The measured and calculated dielectricconstant of the polystyrene reference was ∈=2.55 at 10,000 Hz, which isin good agreement with the reported value (∈˜2.5), refer to J. R.Wunsch, Polystyrene-Synthesis, Production and Applications, Rapra ReviewReports, 2000, Volume 10, No. 4, page 32.

OTFT Fabrication Method

A substrate (either glass or a polymer substrate such as PEN) ispatterned with Au source drain electrodes either by a process of thermalevaporation through a shadow mask or by photolithography (an adhesionlayer of either Cr or Ti is deposited on the substrate prior todeposition of Au). The Au electrodes can the optionally be cleaned usingan 02 plasma cleaning process. A solution of organic semiconductor inbinder is then applied by spin coating (the sample is flooded with thesolution and the substrate is then spun at 500 rpm for 5 seconds then1500 rpm for 1 minute). The coated substrate is then dried in air on ahot stage. The dielectric material, for example 3 wt % PTFE-AF 1600(Sigma-Aldrich cat #469610) dissolved in FC-43) was then applied to thesubstrate by spin coating (sample flooded then spun at 500 rpm for 5seconds then 1500 rpm for 30 seconds). The substrate was then dried inair on a hot stage (100° C. for 1 minute). A gate electrode (Au) is thendefined over the channel area by evaporation through a shadow mask.

The mobility of the OTFT for the binders is characterised by placing ona manual probe station connected to a Keithley SCS 4200 semiconductoranalyzer. The source drain voltage (V_(DS)) is set at −2V (linear) or−40V (saturation) and the gate voltage (V_(G)) scanned from +20V to−60V. Drain current is measured and mobility calculated from thetransconductance.

The mobility of the OTFT for the formulations is characterised byplacing on a semi-auto probe station connected to a Keithley SCS 4200semiconductor analyzer. The source drain voltage is set at −2V and thegate voltage scanned from +20V to −40V. Drain current is measured andmobility calculated from the transconductance.

In linear regime, when |V_(G)>|V_(DS), the source-drain current varieslinearly with V_(G). Thus the field effect mobility (μ) can becalculated from the gradient (S) of I_(DS) vs. V_(G) given by equation 1(where C_(i) is the capacitance per unit area, W is the channel widthand L is the channel length):

$\begin{matrix}{S = \frac{\mu \; {WC}_{i}V_{DS}}{L}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In the saturation regime, the mobility is determined by finding theslope of I_(DS) ^(1/2) VS. V_(G) and solving for the mobility (Equation2)

$\begin{matrix}{I_{DS} \approx \frac{{WC}_{i}{\mu \left( {V_{GS} - V_{T}} \right)}^{2}}{2\; L}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

The following examples are intended to explain the invention withoutrestricting it. The methods, structures and properties described hereincan also be applied to materials that are claimed in this invention butnot explicitly described in the examples.

Compound (1): Preparation of 4-bromobenzene-1,2-dimethanol

A solution of lithium aluminium anhydride (Sigma-Aldrich 593702, 2Msolution in THF, 100 mL, 200 mmol) in THF (Sigma-Aldrich 401757, 300 mL)was cooled in an ice-water bath. A solution of 4-bromophthalic anhydride(Fluorochem 009065, 45.40 g, 200 mmol) in THF (200 mL) was addeddropwise over 4 hours. The reaction mixture was then allowed to stir for6 hours. The ice-water bath was then removed and the mixture allowed towarm to room temperature overnight. The mixture was then cooled in anice-water bath. Water (7.6 mL) was added dropwise. 15% NaOH solution(7.6 mL) was then added dropwise. A further quantity of water (22.8 mL)was added. The ice-water bath was removed and the reaction mixtureallowed to stir for 1 hr. The mixture was then filtered and the filtercake washed with THF 3×200 mL). The filtrates were combined, dried overMgSO₄, filtered and concentrated to give a pale yellow oil whichsolidified on standing (31.48 g). The crude product was purified bycrystallisation from dichloromethane to give the product (1) as acolourless solid (23.50 g, 108 mmol, 54%). ¹H NMR (600 MHz, DMSO-d6)10.52 (1H, s), 10.46 (1H, s), 8.11-8.10 (1H, m), 7.92-7.84 (2H, m).

Compound (2): Preparation of 4-bromo-1,2-benzenedicarboxaldehyde

Oxalyl chloride (Sigma-Aldrich 08801, 24.0 g, 176 mmol) indichloromethane (200 mL) was stirred at −78 deg C. A mixture ofdimethylsulfoxide (29.92 g, 384 mmol) and dichloromethane (50 mL) wasadded dropwise over 60 minutes. A solution of4-bromobenzene-1,2-dimethanol (1) (17.36 g, 80.0 mmol) indichloromethane (10 mL) and dimethylsulfoxide (10 mL) was added dropwiseover 30 minutes. The reaction mixture was stirred for 30 minutes.Triethylamine (Sigma-Aldrich T0886, 200 mL, 1438 mmol) was added over 80minutes. The reaction mixture was then allowed to warm to roomtemperature with stirring overnight. Water (400 mL) was then added. Theorganic layer was separated and the aqueous layer extracted withdichloromethane (2×200 mL). The organic layers were combined, dried overMgSO₄, filtered and concentrated in vacuo to give a pale orange solid(19.12 g). The material was purified by dry column chromatography(gradient elution:heptane:10% ethyl actate:heptane) to give the product(2) as a pale brown solid (14.98 g, 70.3 mmol, 88%). ¹H NMR (600 MHz,CDCl₃) 10.52 (1H, s), 10.46 (1H, s), 8.11-8.10 (1H, m), 7.92-7.84 (2H,m).

Compound (3):2,9-dibromo-6,13-pentacenedione/2,10-dibromo-6,13-pentacenedione

4-bromo-1,2-benzendicarboxaldehyde(2) (14.87 g, 698 mmol, 2 eq) and1,4-cyclohexanedione (Aldrich 125423, 3.91 g, 349 mmol, 1 eq) werecharged to a 2 L round bottom flask. Methylated spirits (74O.P., Fisher11482874, 1000 mL) was added and the mixture stirred at roomtemperature. 5% sodium hydroxide solution (22.0 mL, 275 mmol) was thenadded. A dark brown precipitate formed rapidly. The reaction mixture wasthen heated to 60 deg C. and the mixture stirred at 60 deg C. for 1 h.The mixture was then cooled to ˜18 deg C. The solid was collected byfiltration under suction. The filter cake was washed sequentially withwater (200 mL), methylated spirits (74O.P., 400 mL) and diethyl ether(400 mL). The solid was then dried in a vacuum oven to give the product(3) as an orange/brown solid (13.56 g, 82%). MS (ASAP) m/z 466 (M⁺,100%).

Compound (4):2,9-dibromo-6,13-bis(triisopropylsilylacetylene)pentacenedione-2,10-dibromo-6,13-bis(triisopropylsilylacetylene)pentacene

Triisopropylsilyl acetylene (Fluorochem S18000, 22.5 g, 100 mmol, 6.2eq) was added dropwise to a solution of isopropylmagnesium chloride (2Min THF, Aldrich 230111, 50.25 mL, 100 mmol, 6.2 eq) in THF(Sigma-Aldrich 401757, 150 mL) at room temperature. The solution wasthen heated to 60 deg C. and stirred at this temperature for 45 minutes.The mixture was then cooled to 20 de C.2,9-Dibromo-6,13-pentacenedione/2,10-dibromo-6,13-pentacenedione(3)(7.50 g, 16.1 mmol, 1 eq) was then added and the reaction mixture heatedto 60 deg C. and stirred overnight. The reaction mixture was then cooledto 20 deg C. A solution of tin (II) chloride dihydrate (Sigma-Aldrich208256, 36.30 g) in 10% HCl (165 mL) was added dropwise. The reactionmixture was then heated to 50 deg C. and stirred for 1 hr. The reactionmixture was then cooled to <10 deg C. and the solid collected byfiltration. The filter cake was washed with acetone (2×100 mL) to give agrey solid (6.58 g). The solid was then purified by flash columnchromatography (gradient elution: heptane; 10%-50% DCM:heptane) to givetwo crops; the first crop was then dissolved in DCM (50 mL), acetone(200 mL) was added and the product (4) collected by filtration (2.15 g).The second crop was purified by flash column chromatography andprecipitation as described above to give the product (4) as a blue solid(1.70 g; total mass=3.85 g, 4.27 mmol, 27%). ¹H NMR (500 MHz, CDCl₃)9.26 (2H, s), 9.25 (2H, s), 9.19 (2H, s), 9.17 (2H, s), 8.13 (4H, s),7.83 (4H, d, J=9.1 Hz), 7.45 (4H, d, J=9.1 Hz), 1.46-1.35 (84H, m).

Compound (5): Preparation of N,N-diphenyl-2,4-dimethylphenylamine

Diphenylamine (Sigma-Aldrich 242586, 36.50 g, 216 mmol, 1 eq),4-iodo-m-xylene (Fluorochem 001771, 100.11 g, 431 mmol, 2 eq),1,10-phenanthroline (Sigma-Aldrich 131377, 7.77 g, 43.1 mmol, 0.2 eq)and o-xylene (Sigma-Aldrich 95662, 150 mL) were charged to a roundbottom flask. The reaction mixture was heated to 120 deg C. After 1 hourcopper (I) chloride (Sigma-Aldrich 212946, 4.27 g, 43.1 mmol, 0.2 eq)and KOH (Sigma-Aldrich 484016, 96.82 g, 1726 mmol, 4 eq) were added andthe reaction mixture heated to 160 deg C. and stirred overnight. Themixture was allowed to cool and DCM (200 mL) was added. The mixture wasthen filtered through a pad of celite. Water (200 mL) was added to thefiltrate, the layers were separated and the organic phase washed withwater (200 mL). The aqueous phases were back-extracted with DCM (200 mL)and the combine organic extracts were dried over MgSO₄, filtered andconcentrated in vacuo to give a viscous dark brown-black oil (72.43 g).The crude product was purified by dry column chromatography (eluent:heptane) (55.10 g) followed by recrystallization from methanol to givethe product (5) as a colourless crystalline solid (45.56 g, 84%). ¹H NMR(500 MHz, CDCl₃) 7.25-6.88 (13H, m), 2.35 (3H, s), 2.02 (3H, s).

Compound (6): Preparation ofN,N-bis(4-bromophenyl)-2,4-dimethylphenylamine

A solution N, N-diphenyl-2,4-dimethylphenylamine (40.00, 146 mmol, 1 eq)in DMF (200 mL) was cooled to −60 deg C. A solution ofN-bromosuccinimide (Sigma-Aldrich B81255, 52.08 g, 293 mmol, 2 eq) inDMF (260 mL) was added over 30 minutes, then the mixture was allowed towarm to room temperature. After 2 hours the reaction mixture was pouredinto water (2.4 L). The mixture was extracted with heptane (4×800 mL),the organic extracts were dried over MgSO₄, filtered and concentrated invacuo to give a colourless solid (61.92 g). The product wasrecrystallized from methanol/acetone (1:1 mixture) to give the product(6) as a colourless crystalline solid (57.13 g, 91%). ¹H NMR (500 MHz,CDCl₃) 7.28 (4H, d, J=8.8 Hz), 7.07-6.95 (3H, m), 6.82 (4H, d, J=8.8Hz), 2.34 (3H, s), 1.98 (3H, s).

Compound (7): Preparation ofN,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-2,4-dimethylphenylamine

A stirred solution of N,N-bis(4-bromophenyl)-2,4-dimethylphenylamine (6)(10.00 g, 23.2 mmol, 1 eq) in THF (Sigma-Aldrich 401757, 40 mL) undernitrogen was cooled to −65 deg C. n-Butyllithium (Acros 10181852, 2.5Msolution in hexanes, 22.3 mL, 55.7 mmol, 2.4 eq) was added dropwise andthe reaction mixture was then stirred for 1 h.2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (Sigma-Aldrich417149, 11.22 g, 60.3 mmol, 2.6 eq) was added dropwise. The reactionmixture was then allowed to warm to room temperature overnight. Water(60 mL) was added and the mixture stirred for 20 minutes. The mixturewas then extracted with dichloromethane (3×60 mL). The combined organicextracts were dried over MgSO₄, filtered and concentrated in vacuo togive a yellow foam (11.27 g). The product was then purified by drycolumn chromatography (gradient elution 5%-10% EtOAc:heptane) to give acolourless solid (6.65 g). This was recrystallized from MeCN/THF to givethe product (7) as a colourless crystalline solid (6.14 g, 11.7 mmol,50%). ¹H NMR (500 MHz, CDCl₃) 7.63 (4H, d, J=8.3 Hz), 7.06-6.99 (3H, m),6.96 (4H, d, J=8.3 Hz), 2.34 (3H, s), 1.96 (3H, s), 1.32 (24H, s). MS(ASAP) m/z 525 (M⁺, 100%).

Compound (8): Preparation of N,N-diphenyl-4-methoxyphenylamine

Diphenylamine (Sigma-Aldrich 242586, 36.50 g, 216 mmol, 1 eq),4-iodoanisole (Sigma-Aldrich I7608, 100.96 g, 431 mmol, 2 eq),1,10-phenanthroline (Sigma-Aldrich 131377, 7.77 g, 43.1 mmol, 0.2 eq)and xylene (150 mL) were charged to a round bottom flask. The reactionmixture was heated to 120 deg C. After 1 hour copper (I) chloride(Sigma-Aldrich 212946, 4.27 g, 43.1 mmol, 0.2 eq) and KOH (Sigma-Aldrich484016, 96.82 g, 1726 mmol, 4 eq) were added and the reaction mixtureheated to 160 deg C. and stirred overnight. The mixture was allowed tocool, then water (250 mL) and DCM (200 mL) were then added. The mixturewas then filtered through a pad of celite. The mixture was separated andthe organic phase washed with water (200 mL). The aqueous phases wereback-extracted with DCM (200 mL) and the combine organic extracts weredried over MgSO₄, filtered and concentrated in vacuo to give a viscousdark brown-black oil (80.20 g). The crude product was purified by drycolumn chromatography (gradient elution: heptane, 5-10% DCM:heptane)followed by recrystallization from methanol to give the product (8) as acolourless crystalline solid (52.60 g, 89%). ¹H NMR (500 MHz, CDCl₃)7.25-6.82 (14H, m), 3.81 (3H, s, OCH ₃).

Compound (9): Preparation of N,N-bis(4-bromophenyl)-4-methoxyphenylamine

A solution of N, N-diphenyl-4-methoxyphenylamine (8) (40.00, 146 mmol, 1eq) in DMF (240 mL) was cooled to −60 deg C. A solution ofN-bromosuccinimide (51.71 g, 291 mmol, 2 eq) in DMF (260 mL) was addedover 30 minutes, then the mixture was allowed to warm to roomtemperature. After 2 hours the reaction mixture was poured into water(2.4 L). The mixture was extracted with heptane (4×800 mL), the organicextracts were dried over MgSO₄, filtered and concentrated in vacuo togive a brown oil (65.12). The product was purified by dry columnchromatography (eluent: heptane) to give the product as a colourlesssolid (52.36 g, 52%). ¹H NMR (500 MHz, CDCl₃) 7.30 (4H, d, J=8.7 Hz),7.02 (2H, d, J=8.7 Hz), 6.8 (4H, d, J=8.7 Hz), 6.84 (2H, d, J=8.7 Hz),3.80 (3H, s, OCH ₃).

Compound (10): Preparation ofN,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-phenylamine

A stirred solution of N,N-bis(4-bromophenyl)-4-methoxyphenylamine (9)(15.00 g, 34.6 mmol, 1 eq) in THF (Sigma-Aldrich 401757, 60 mL) undernitrogen was cooled to −65 deg C. n-Butyllithium (Acros 213358000, 2.5Msolution in hexanes, 33.2 mL, 2.4 eq) was added dropwise and thereaction mixture was then stirred for 1 h.2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (Sigma-Aldrich417149, 16.75 g, 90.0 mmol, 2.6 eq) was added dropwise. The reactionmixture was then allowed to warm to room temperature overnight. Water(90 mL) was added and the mixture stirred for 20 minutes. The mixturewas then extracted with dichloromethane (5×90 mL). The combined organicextracts were dried over MgSO₄, filtered and concentrated in vacuo togive a yellow foam (16.01 g). The product was then purified by drycolumn chromatography (gradient elution 5%-15% EtOAc:heptane) to givethe product as colourless solid (7.31 g, 13.9 mmol, 40%). ¹H NMR (500MHz, CDCl₃) 7.66 (4H, d, J=6.8 Hz), 7.06 (2H, d, J=8.9 Hz), 7.02 (4H, d,J=6.8 Hz), 3.81 (3H, s, OCH₃), 1.33 (24H, s).

Compound (11): Preparation ofbis(N-4-chlorophenyl)-2,4-dimethoxyphenylamine

A mixture of 2,4-dimethoxyaniline (TCI Europe D1982, 60.00 g, 391 mmol),1-chloro-4-iodobenzene (233.51 g, 979 mmol), anhydrous potassiumcarbonate (194.89 g, 1410 mmol), copper powder (71.48 g, 1.12 mmol),18-crown-6 ether (25.88 g, 97.9 mmol) and anhydrous o-DCB (100 mL) werecharged to a 700 mL flange flask, fitted with a Dean-Stark trap,thermometer, overhead stirrer and water condenser, and flushed withnitrogen for 10 minutes. The mixture was heated to between 170 deg C.After 3 hr the mixture was allowed to cool to room temperature, DCM (500mL) was added and the mixture filtered through a GF/A filter paper. Thecake washed with DCM (200 mL). The combined filtrates were washed withwater (250 mL×2) and the combined aqueous layers back-extracted with DCM(200 mL×2). The organic layers were combined, dried over MgSO₄ (30minutes) and filtered. The filter cake was washed with further DCM (150mL×2) and the combined filtrates concentrated in vacuo to give a brownsemi-solid (181.11 g). The crude product was dry loaded onto silica geland purified by dry flash column chromatography (gradient elution:heptanes-15% DCM:heptane) to give a colourless solid (72.95 g). Theproduct was recystallised from heptane to give a colourless crystallinesolid (11) (62.89 g, 43%). ¹H NMR (500 MHz) 7.13 (2H, d, J=8.8 Hz), 7.06(2H, d, J=9.0 Hz), 6.89 (2H, d, J=8.8 Hz), 6.54 (1H, d, J=2.5 Hz), 6.49(2H, m), 3.83 (3H, s), 3.65 (3H, s)

Compound (12): Preparation of N,N-diphenyl-2,4-dimethoxyphenylamine

A solution of N,N-bis(4-chlorophenyl)-2,4-dimethoxyphenylamine (10.0 g,26.7 mmol, 1 eq) in toluene (100 mL) was stirred at room temperatureunder N₂. Ammonium formate (Sigma-Aldrich 156264, 20 g, 317 mmol) and10% Pd on activated charcoal (Sigma-Aldrich 75993, 50% water content,5.0 g) was added and the mixture heated to 65 deg C. overnight. Afurther portion of ammonium formate (30 g, 476 mmol) and 10% Pd on C (5g) were added and the mixture stirred at 65 deg C. for 2h. The reactionmixture was allowed to cool and then filtered (Whatman GF/F filter)under suction using a Buchner funnel. The filtrate was then washed withwater. The organic layer was then dried over MgSO₄, filtered andconcentrated to give the product (12) as colourless solid (8.16 g,100%). ¹H NMR (500 MHz, CDCl₃) 7.20-6.90 (10H, m), 6.55-6.48 (3H, m),3.83 (3H, s), 3.65 (3H, s).

Compound (13): Preparation ofN,N-bis(4-bromophenyl)-2,4-dimethoxyphenylamine

A solution of N,N-diphenyl-2,4-dimethoxyphenylamine(12) (8.00 g, 26.2mmol, 1 eq) in DMF (Sigma-Aldrich 227056, 140 mL) was stirred at −60 degC. under N₂. A solution of N-bromosuccinimide (Sigma-Aldrich B81255,9.50 g, 53.4 mmol, 2 eq) was added dropwise. The mixture was thenallowed to warm to room temperature. After 2h the reaction mixture wasthen poured into a stirred mixture of water (1 L) and heptane (500 mL).The organic layer was separated and the aqueous extracted with heptane(3×500 mL) The heptane extracts were washed with water (500 mL), driedover MgSO₄, filtered and concentrated in vacuo to give a red-orangesolid (9.40 g). The product was purified by dry column chromatography(gradient elution: heptane; 5%-20% DCM:heptane) to give the product as acolourless solid (9.28 g, 76%). ¹H NMR (300 MHz, CDCl₃) 7.28 (4H, d,J=6.0 Hz), 7.06-7.04 (1H, m), 6.86 (4H, d, J=6.0 Hz), 6.55-6.48 (2H, m),3.85 (3H, s), 3.66 (3H, s).

Compound (14): Preparation ofN,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-2,4-methoxyphenylamine

A solution of N,N-bis(4-bromophenyl)-2,4-dimethoxyphenylamine(13) (6.00g, 13.0 mmol, 1 eq) in THF (Sigma-Aldrich 401757, 30 mL) under N₂ wascooled to −70 deg C. n-Butyllithium (Acros 213358000, 2.5M in hexanes,14.1 mL, 35.3 mmol, 2.7 eq) was added dropwise and the mixture stirredfor 1 h. 2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(Sigma-Aldrich 417149, 6.80 g, 36.5 mmol, 2.8 eq) was added dropwise.The reaction mixture was then allowed to warm to room temperature withstirring overnight. Water (40 mL) was then added, the organic layer wasseparated and the aqueous layer extracted with DCM (5×40 mL). Thecombined organic extracts were dried over MgSO₄, filtered andconcentrated in vacuo to give a yellow oil (7.30 g). The product waspurified by dry column chromatography (gradient elution: heptane; 5%-15%EtOAc:heptane) to give the product (14) as a colourless solid (2.81 g,5.0 mmol, 39%). ¹H NMR (300 MHz, CDCl₃) 7.63 (4H, d, J=8.6 Hz),7.07-7.04 (1H, m), 6.97 (4H, d, J=8.6 Hz), 6.54-6.46 (2H, m), 3.82 (3H,s), 3.60 (3H, s).

PAHC Copolymer (1): Preparation of TIPSpentacene-2,4-dimethyltriarylamine copolymer

A mixture of2,9-dibromo-6,13-bis(triisopropylsilylacetylene)pentacenedione/2,10-dibromo-6,13-bis(triisopropylsilylacetylene)pentacene(4)(0.39 g, 0.49 mmol, 0.5 eq),N,N-bis(4-bromophenyl)-2,4-dimethylphenylamine(6) (0.21 g, 0.49 mmol,0.5 eq) N,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-2,4-dimethylphenylamine(7) (0.52 g, 0.98mmol, 1 eq) tetrakis(triphenylphosphine)palladium (0) (Acros 12065360,0.034 g, 0.03 mmol, 0.03 eq), 2M K₂CO₃ (2.9 mL, 5.88 mmol, 6 eq) andAliquat® 336 (Sigma-Aldrich 205613, 6 drops) in toluene (42 mL) wasdegassed by passing a stream of nitrogen through the solution for 30minutes. The mixture was then heated to reflux. After 1 hour HPLCconfirmed the presence of oligomers. The reaction mixture was allowed tocool to 50 deg C. The reaction mixture was poured into MeOH (135 mL)with stirring. After 30 minutes the precipitated solid was collected byfiltration under suction using a Buchner funnel to give a brown powder(1.20 g). The solid was purified by flash column chromatography (eluent:toluene). The fractions containing the product were concentrated invacuo to give a dark purple solid (0.45 g). The solid was slurried inmethanol (5 mL) and the solid collected by filtration under suctionusing a Buchner funnel. The solid was then dried in a vacuum oven togive the product as a dark purple solid (0.32 g)(75%2,4-dimethyltriarylamine:25% TIPS pentacene) which was characterised asfollows: GPC Mn=5033 Daltons, N_(av)=14.

Permittivity of the TIPS pentacene-2,4-dimethyltriarylamine copolymer(1) was 2.96.

(As a comparison, the permittivity of commercially available2,4-dimethylpolytriarylamine (High Force Research Ltd Code for the2,4-dimethyl polytriarylamine polymer, PE3) purchased from High ForceResearch Ltd was measured, in our permittivity tests the binder PE3 hada permittivity of 2.98).

Formulation 1

TIPS pentacene-2,4-dimethyltriarylamine copolymer, PAHC (1) andpolyacene 1, (1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene) (70:30 ratio by weight) were dissolved in1,2,3,4-tetrahydronaphthalene at 1.7 wt. % total solids. This was coatedas an organic semiconductor layer in an OTFT according to the methoddescribed above. The formulation was spin coated (500 rpm for 5s, then1500 rpm for 60s) onto patterned Au source/drain electrodes (50 nm thickAu treated with a 10 mM solution of pentafluorobenzene thiol inisopropyl alcohol). The fluoropolymer dielectric Cytop (Asahi ChemicalCo.) was spin coated on top (500 rpm for 5s then 1500 rpm for 20s).Finally an Au gate electrode was deposited by shadow mask evaporation.

Mobility in the OTFT was 1.1 cm²V⁻¹s⁻¹ at channel length L=4 m, (linearmobility).

Mobility in the TFT was 2.2 cm²V⁻¹s⁻¹ at channel length L=30 m, (linearmobility).

PAHC Copolymer (2): Preparation of TIPS pentacene-4-methoxytriarylaminecopolymer

A mixture of2,9-dibromo-6,13-bis(triisopropylsilylacetylene)pentacenedione/2,10-dibromo-6,13-bis(triisopropylsilylacetylene)pentacene(4)(0.39 g, 0.49 mmol, 0.5 eq),N,N-bis(4-bromophenyl)-4-methoxyphenylamine(9) (0.21 g, 0.49 mmol, 0.5eq)N,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-methoxyphenylamine(10)(0.52 g, 0.98 mmol, 1 eq) tetrakis(triphenylphosphine)palladium (0)(Acros 12065360, 0.034 g, 0.03 mmol, 0.03 eq), 2M K₂CO₃ (2.9 mL, 5.88mmol, 6 eq) and Aliquat® 336 (6 drops) in toluene (42 mL) was degassedby passing a stream of nitrogen through the solution for 30 minutes. Themixture was then heated to reflux. After 30 minutesHPLC confirmed thepresence of oligomers. The reaction mixture was allowed to cool to 50deg C. The reaction mixture was poured into MeOH (135 mL) with stirring.After 30 minutes the precipitated solid was collected by filtrationunder suction using a Buchner funnel to give a brown powder (0.67 g).The solid was purified by flash column chromatography (eluent: THF). Thefractions containing the product were concentrated in vacuo to give adark purple solid (0.67 g). The solid was dissolved in THF (10 mL) andpoured into methanol (30 mL). The precipitated solid was collected byfiltration under suction using a Buchner funnel. The solid obtained wasthen dried in a vacuum oven to give the product as a dark green powder(0.59 g)(75% 4-methoxytriarylamine: 25% TIPS pentacene) which wascharacterised as follows: GPC Mn=4680 Daltons, N_(av)=13.

Permittivity of the TIPS pentacene-4-methoxytriarylamine copolymer (2)was 3.26.

Formulation 2

TIPS pentacene-2,4-dimethoxytriarylamine copolymer, PAHC (2) andpolyacene 1, (1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene) (70:30 ratio by weight) were dissolved in1,2,3,4-tetrahydronaphthalene at 1.7 wt. % total solids. This was coatedas an organic semiconductor layer in an OTFT according to the methoddescribed above. The formulation was spin coated (500 rpm for 5s, then1500 rpm for 60s) onto patterned Au source/drain electrodes (50 nm thickAu treated with a 10 mM solution of pentafluorobenzene thiol inisopropyl alcohol). The fluoropolymer dielectric Cytop (Asahi ChemicalCo.) was spin coated on top (500 rpm for 5s then 1500 rpm for 20s).Finally an Au gate electrode was deposited by shadow mask evaporation.

Mobility in the OTFT was 0.98 cm²V⁻¹s⁻¹ at channel length L=30 m,(linear mobility).

PAHC Copolymer (3): Preparation of TIPSpentacene-2,4-dimethoxytriarylamine copolymer

A mixture of2,9-dibromo-6,13-bis(triisopropylsilylacetylene)pentacenedione/2,10-dibromo-6,13-bis(triisopropylsilylacetylene)pentacene(4)(0.43 g, 0.54 mmol, 0.5 eq),N,N-bis(4-bromophenyl)-2,4-dimethoxyphenylamine(13) (0.25 g, 0.54 mmol,0.5 eq)N,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-2,4-dimethoxyphenylamine(14)(0.60 g, 1.08 mmol, 1 eq) tetrakis(triphenylphosphine)palladium (0)(Acros 12065360, 0.037 g, 0.03 mmol, 0.03 eq), 2M K₂CO₃ (3.2 mL, 6.48mmol, 6 eq) and Aliquat® 336 (7 drops) in toluene (50 mL) was degassedby passing a stream of nitrogen through the solution for 30 minutes. Themixture was then heated to reflux. After 30 minutes HPLC confirmed thepresence of oligomers. The reaction mixture was allowed to cool to 50deg C. The reaction mixture was poured into MeOH (150 mL) with stirring.After 30 minutes the precipitated solid was collected by filtrationunder suction using a Buchner funnel to give a brown powder (0.87 g).The solid was purified by flash column chromatography (eluent: THF). Thefractions containing the product were concentrated in vacuo to give adark purple solid (0.73 g). The solid was purified again by flash columnchromatography (eluent: THF). The fractions containing the product wereconcentrated in vacuo to give a dark purple solid (0.47 g). The solidwas dissolved in THF (10 mL) and poured into methanol (30 mL). Theprecipitated solid was collected by filtration under suction using aBuchner funnel. The solid obtained was then dried in a vacuum oven togive the product as a dark green powder (0.45 g) (75%2,4-dimethoxytriarylamine:25% TIPS pentacene) which was characterised asfollows: GPC Mn=5079 Daltons, N_(av)=13.

Permittivity of the TIPS pentacene-4-methoxytriarylamine copolymer (3)was 3.10.

Formulation 3

TIPS pentacene-2,4-dimethoxytriarylamine copolymer, PAHC (3) andpolyacene 1, (1,4,8,11-tetramethyl-6,13-bis(triethylsilylethynyl)pentacene) (70:30 ratio by weight) were dissolved in1,2,3,4-tetrahydronaphthalene at 1.7 wt. % total solids. This was coatedas an organic semiconductor layer in an OTFT according to the methoddescribed above. The formulation was spin coated (500 rpm for 5s, then1500 rpm for 60s) onto patterned Au source/drain electrodes (50 nm thickAu treated with a 10 mM solution of pentafluorobenzene thiol inisopropyl alcohol). The fluoropolymer dielectric Cytop (Asahi ChemicalCo.) was spin coated on top (500 rpm for 5s then 1500 rpm for 20s).Finally an Au gate electrode was deposited by shadow mask evaporation.

Mobility was 0.7 cm²V⁻¹s⁻¹ (linear mobility, at channel length 10=μm).

Mobility in the OTFT was 1.4 cm²V⁻¹s⁻¹ at channel length 30=μm, (linearmobility).

Particularly preferred PAHCs according to the present invention areshown in the following table:

Preferred PAHCs        

Case 1 R^(′a), R^(′b), R^(′c), R^(′d), R^(′e) = H R⁶ = R¹³ =trimethylsilyl ethynyl; R¹, R², R³, R⁴, R⁵, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹²,and R¹⁴ = H; and R³ and, R⁹ are bonds to another unit of Monomer (A) or(B) Case 2 R⁶ = R¹³ = triisopropyllsilylethynyl

Case 4 R⁶ = R¹³ = triisopropyllsilylethynyl; and R¹, R⁴, R⁸, R¹¹ = C₁ toC₄ alkyl (e.g. methyl) Case 5 R⁶ = R¹³ = triisopropyllsilylethynyl; andR¹, R⁴, R⁸, R¹¹ = C₁ to C₄ alkoxy (e.g. methoxy) Case 6 R⁶ = R¹³ =triethylsilylethynyl

Case 1 R^(′b), R^(′d), R^(′e) = H Case 2 Case 3 R^(′a) and R^(′c) = C₁to C₄ alkyl Case 4 Case 5 Case 6 Case 7 Case 1 Case 2 R^(′b), R^(′c),R^(′d), R^(′e) = H Case 3 R^(′a) = C₁ to C₆ alkoxy Case 4 Case 5 (i)R^(′a) = methoxy Case 6 (ii) R^(′a) = ethoxy Case 7 Case 1 R^(′a),R^(′b), R^(′d), R^(′e) = H Case 2 R^(′c) = C₁ to C₆ alkoxy Case 3 Case 4(i) R^(′c) = methoxy Case 5 (ii) R^(′c) = ethoxy Case 6 Case 7 Case 1R^(′a), R^(′b), R^(′c), R^(′d) = H Case 2 R^(′e) = C₁ to C₆ alkoxy Case3 Case 4 (i) R^(′e) = methoxy Case 5 (ii) R^(′e) = ethoxy Case 6 Case 7Case 1 R^(′b), R^(′d), R^(′e) = H Case 2 R^(′a) = R^(′c) = C₁ to C₆alkoxy Case 3 Case 4 (i) R^(′a) = R^(′c) = methoxy Case 5 (ii) R^(′a) =R^(′c) = ethoxy Case 6 Case 7 Case 1 R^(′b), R^(′d) = H Case 2 R^(′a),R^(′c), R^(′e) = C₁ to C₆ Case 3 alkoxy Case 4 Case 5 (i) R^(′a),R^(′c), R^(′e) = methoxy Case 6 Case 7 (ii) R^(′a), R^(′c), R^(′e) =ethoxy Case 1 R^(′b), R^(′d) = H Case 2 R^(′b), R^(′c), R^(′d) = C₁ toC₆ Case 3 alkoxy Case 4 Case 5 (i) R^(′b), R^(′c), R^(′d) = methoxy Case6 (ii) R^(′b), R^(′c), R^(′d) = ethoxy Case 7 Case 1 R^(′b), R^(′c),R^(′d), R^(′e) = H Case 2 Case 3 R^(′a) = Cyano (CN) Case 4 Case 5 Case6 Case 7 Case 1 R^(′b), R^(′c), R^(′d), R^(′e) = H Case 2 R^(′a) =Isopropylcyano group Case 3 Case 4 Case 5 Case 6 Case 7

Case 1 R^(′a), R^(′b), R^(′d), R^(′e) = H Case 2 R^(′c) = Isopropylcyanogroup Case 3 Case 4 Case 5 Case 6 Case 7

The organic semiconductors compounds specified in the table areparticularly preferred as they combine the beneficial properties of highcharge transport mobility (of the binders) with a polarity that is morecompatible with benign, non-chlorinated solvents that will be desirablefor use in large area printing. In addition, as these compounds are morepolar once deposited as the OSC layer, or alternatively as a componentin the OSC layer, they are expected to be resistant to beingre-dissolved by the hydrophobic solvents used for the organic gateinsulators (OGI) such as Cytop. Furthermore, it is expected that thepolar binders are useful for both top gate and bottom gate OTFTs,particularly for bottom gate OTFTs.

1. A Polycyclic Aromatic Hydrocarbon Copolymer (PAHC) comprising amixture of at least one polyacene monomer unit having the Formula (A)and at least one monomer unit having the Formula (B):

wherein each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³and R¹⁴, which may be the same or different, independently representshydrogen; a branched or unbranched, substituted or unsubstituted C₁-C₄₀alkyl group; a branched or unbranched, substituted or unsubstitutedC₂-C₄₀ alkenyl group; a branched or unbranched, substituted orunsubstituted C₂-C₄₀ alkynyl group; an optionally substituted C₃-C₄₀cycloalkyl group; an optionally substituted C₆-C₄₀ aryl group; anoptionally substituted C₁-C₄₀ heterocyclic group; an optionallysubstituted C₁-C₄₀ heteroaryl group; an optionally substituted C₁-C₄₀alkoxy group; an optionally substituted C₆-C₄₀ aryloxy group; anoptionally substituted C₇-C₄₀ alkylaryloxy group; an optionallysubstituted C₂-C₄₀ alkoxycarbonyl group; an optionally substitutedC₇-C₄₀ aryloxycarbonyl group; a cyano group (—CN); a carbamoyl group(—C(═O)NR¹⁵R¹⁶); a carbonyl group (—C(═O)—R¹⁷); a carboxyl group(—CO₂R¹⁸) a cyanate group (—OCN); an isocyano group (—NC); an isocyanategroup (—NCO); a thiocyanate group (—SCN) or a thioisocyanate group(—NCS); an optionally substituted amino group; a hydroxy group; a nitrogroup; a CF₃ group; a halo group (Cl, Br, F, I); —SR¹⁹; —SO₃H; —SO₂R²⁰;—SF₅; an optionally substituted silyl group; a C₂-C₁₀ alkynyl groupsubstituted with a —SiH₂R²² group, a C₂-C₁₀ alkynyl substituted with a—SiHR²²R²³ group, or a C₂-C₁₀ alkynyl moiety substituted with a—Si(R²²)_(x)(R²³)_(y)(R²⁴)_(z) group; wherein each R²² group isindependently selected from the group consisting of a branched orunbranched, substituted or unsubstituted C₁-C₁₀ alkyl group, a branchedor unbranched, substituted or unsubstituted C₂-C₁₀ alkynyl group, asubstituted or unsubstituted C₂-C₂₀ cycloalkyl group, a substituted orunsubstituted C₂-C₁₀ alkenyl group, and a substituted or unsubstitutedC₆-C₂₀ cycloalkylalkylene group; each R²³ group is independentlyselected from the group consisting of a branched or unbranched,substituted or unsubstituted C₁-C₁₀ alkyl group, a branched orunbranched, substituted or unsubstituted C₂-C₁₀ alkynyl group, asubstituted or unsubstituted C₂-C₁₀ alkenyl group, a substituted orunsubstituted C₂-C₂₀ cycloalkyl group, and a substituted orunsubstituted C₆-C₂₀ cycloalkylalkylene group; R²⁴ is independentlyselected from the group consisting of hydrogen, a branched orunbranched, substituted or unsubstituted C₂-C₁₀ alkynyl group, asubstituted or unsubstituted C₂-C₂₀ cycloalkyl group, a substituted orunsubstituted C₆-C₂₀ cycloalkylalkylene group, a substituted C₅-C₂₀ arylgroup, a substituted or unsubstituted C₆-C₂₀ arylalkylene group, anacetyl group, a substituted or unsubstituted C₃-C₂₀ heterocyclic ringcomprising at least one of O, N, S and Se in the ring; wherein x=1 or 2;y=1 or 2; z=0 or 1; and (x+y+z)=3; wherein each of R¹⁵, R¹⁶, R¹⁸, R¹⁹and R²⁰ independently represent H or optionally substituted C₁-C₄₀carbyl or hydrocarbyl group optionally comprising one or moreheteroatoms; wherein R¹⁷ represents a halogen atom, H or optionallysubstituted C₁-C₄₀ carbyl or C₁-C₄₀ hydrocarbyl group optionallycomprising one or more heteroatoms; wherein k and 1 are independently 0,1 or 2; wherein at least two of R¹, R², R³, R⁴, R⁸, R⁹, R¹⁰ and R¹¹ area bond, represented by

, to another monomer unit having the Formula (A) or (B), and whereinAr₁, Ar₂ and Ar₃, which may be the same or different, each represent,independently if in different repeat units, an optionally substitutedC₆₋₄₀ aromatic group (mononuclear or polynuclear), wherein preferably atleast one of Ar₁, Ar₂ and Ar₃ is substituted with at least one polar ormore polarising group.
 2. A PAHC according to claim 1, comprising atleast 20 to 40% of monomer (A) and at least 60 to 80% of monomer (B),based on the total of all monomer units (A) and (B) in the copolymer. 3.A PAHC according to claim 1 or claim 2, wherein k=1=0 or
 1. 4-5.(canceled)
 6. A PAHC according to claim 1, wherein the copolymers aresemiconducting copolymers having a permittivity at 1000 Hz of greaterthan 1.5.
 7. A PAHC according to claim 4, wherein the copolymers aresemiconducting copolymers having a permittivity at 1000 Hz of between3.4 and 8.0.
 8. A PAHC according to claim 1, wherein at least one; ofgroups R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³ and R¹⁴are (tri-C₁₋₂₀ hydrocarbylsilyl)C₁₋₄alkynyl- groups.
 9. A PAHC accordingto claim 1, wherein R⁵, R⁷, R¹² and R¹⁴ are hydrogen.
 10. A PAHCaccording to claim 1, wherein —Si(R²²)_(x)(R²³)_(y)(R²⁴)_(z) is selectedfrom the group consisting of trimethylsilyl, triethylsilyl,tripropylsilyl, dimethylethylsilyl, diethylmethylsilyl,dimethylpropylsilyl, dimethylisopropylsilyl, dipropylmethylsilyl,diisopropylmethylsilyl, dipropylethylsilyl, diisopropylethyl silyl,diethylisopropylsilyl, triisopropylsilyl, trimethoxysilyl,triethoxysilyl, triphenylsilyl, diphenylisopropylsilyl,diisopropylphenylsilyl, diphenylethylsilyl, diethylphenylsilyl,diphenylmethylsilyl, triphenoxysilyl, dimethylmethoxysilyl,dimethylphenoxysilyl, and methylmethoxyphenyl.
 11. A PAHC according toclaim 1, having the Formula (A1) or (A2)

wherein R²⁵, R²⁶ and R²⁷ are independently selected from the groupconsisting of C₁-C₆ alkyl and C₂-C₆ alkenyl, preferably independentlyselected from the group consisting of methyl, ethyl, propyl, isopropyl,n-butyl, isobutyl, t-butyl, 1-propenyl and 2-propenyl, more preferablyethyl, n-propyl and isopropyl.
 12. A PAHC according to claim 1, whereinthe polyacene monomer units have the Formulae (A3) and (A4):

wherein R²⁵, R²⁶ and R²⁷ are independently selected from the groupconsisting of methyl, ethyl and isopropyl.
 13. A PAHC according to claim1, wherein the polyacene monomer unit is selected from the followingunits (A5) to (A8):


14. A PAHC according to claim 1, wherein monomer unit (B) having the,Ar₁, Ar₂ and Ar₃, which may be the same or different, each representing,independently if in different repeat units, an optionally substitutedC₆₋₂₀ aromatic group (mononuclear or polynuclear), wherein at least oneof Ar₁, Ar₂ and Ar₃ is substituted with at least one or more polar orpolarising group, and n=1 to
 20. 15. A PAHC according to claim 12wherein the one or more polar or polarising group(s) is independentlyselected from the group consisting of nitro group, nitrile group, C₁₋₄₀alkyl group substituted with a nitro group, a nitrile group, a cyanategroup, an isocyanate group, a thiocyanate group or a thioisocyanategroup; C₁₋₄₀ alkoxy group optionally substituted with a nitro group, anitrile group, a cyanate group, an isocyanate group, a thiocyanate groupor a thioisocyanate group; C₁₋₄₀ carboxylic acid group optionallysubstituted with a nitro group, a nitrile group, a cyanate group, anisocyanate group, a thiocyanate group or a thioisocyanate group; C₂₋₄₀carboxylic acid ester optionally substituted with a nitro group, anitrile group, a cyanate group, an isocyanate group, a thiocyanate groupor a thioisocyanate group; sulfonic acid optionally substituted with anitro group, a nitrile group, a cyanate group, an isocyanate group, athiocyanate group or a thioisocyanate group; sulfonic acid esteroptionally substituted with a nitro group, a nitrile group, a cyanategroup, an isocyanate group, a thiocyanate group or a thioisocyanategroup; cyanate group, isocyanate group, thiocyanate group,thioisocyanate group; and an amino group optionally substituted with anitro group, a nitrile group, a cyanate group, an isocyanate group, athiocyanate group or a thioisocyanate group; and combinations thereof.16. A PAHC according to claim 12, wherein Ar₁, Ar₂ and Ar₃ are allphenyl which may be independently substituted with 1 or 2 groupsselected from methoxy, cyanomethyl, CN and mixtures thereof, and n=1 to10.
 17. A PAHC according to claim 1, further comprising one or moremonomers (C), (D), (D′) and/or (E):

wherein each R^(1′), R^(2′), R^(3′), R^(4′), R^(5′), R^(6′) and R^(7′),each of which may be the same or different, is selected from the samegroup as R¹, R², R³, R⁴, R⁵, R⁶ and R⁷, as defined in claim 1; whereinn′=1 to 3; and wherein monomer (A) is present in an amount of at least20 wt. %; monomer (B) is present in an amount of at least 60 wt. % andthe remainder is comprised of monomers (C), (D), (D′) and/or (E), basedon the total weight of all monomer units in the copolymer.
 18. Anorganic semiconductor composition comprising a PAHC according to claim 1and a polyacene small molecule, wherein the PAHC has a permittivity at1000 Hz of between 3.4 and 8.0, or between 3.4 and 4.5.
 19. (canceled)20. An organic semiconductor composition comprising a PolycyclicAromatic Hydrocarbon Copolymer (PAHC) according to claim 1, wherein thecomposition has a permittivity at 1000 Hz of between 3 and 6.5. 21.(canceled)
 22. An organic semiconductor composition according to claim16 having a charge mobility value of at least 0.5 cm²V⁻¹s⁻¹, preferablybetween 2 and 5.0 cm²V⁻¹s⁻¹.
 23. An organic semiconductor layer orelectronic device, comprising a PAHC or an organic semiconductorcomposition according to any preceding claim. 24-26. (canceled)
 27. Aprocess for producing a Polycyclic Aromatic Hydrocarbon Copolymer (PAHC)comprising copolymerising a composition containing at least onepolyacene monomer unit selected from the structures (A′) and (B′),

wherein each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³and R¹⁴, which may be the same or different, independently representshydrogen; a branched or unbranched, substituted or unsubstituted C₁-C₄₀alkyl group; a branched or unbranched, substituted or unsubstitutedC₂-C₄₀ alkenyl group; a branched or unbranched, substituted orunsubstituted C₂-C₄₀ alkynyl group; an optionally substituted C₃-C₄₀cycloalkyl group; an optionally substituted C₆-C₄₀ aryl group; anoptionally substituted C₁-C₄₀ heterocyclic group; an optionallysubstituted C₁-C₄₀ heteroaryl group; an optionally substituted C₁-C₄₀alkoxy group; an optionally substituted C₆-C₄₀ aryloxy group; anoptionally substituted C₇-C₄₀ alkylaryloxy group; an optionallysubstituted C₂-C₄₀ alkoxycarbonyl group; an optionally substitutedC₇-C₄₀ aryloxycarbonyl group; a cyano group (—CN); a carbamoyl group(—C(═O)NR¹⁵R¹⁶); a carbonyl group (—C(═O)—R¹⁷); a carboxyl group(—CO₂R¹⁸) a cyanate group (—OCN); an isocyano group (—NC); an isocyanategroup (—NCO); a thiocyanate group (—SCN) or a thioisocyanate group(—NCS); an optionally substituted amino group; a hydroxy group; a nitrogroup; a CF₃ group; a halo group (Cl, Br, F, I); —SR¹⁹; —SO₃H; —SO₂R²⁰;—SF₅; an optionally substituted silyl group; a C₂-C₁₀ alkynyl groupsubstituted with a —SiH₂R²² group, a C₂-C₁₀ alkynyl substituted with a—SiHR²²R²³ group, or a C₂-C₁₀ alkynyl moiety substituted with a—Si(R²²)_(x)(R²³)_(y)(R²⁴)_(z) group; wherein each R²² group isindependently selected from the group consisting of a branched orunbranched, substituted or unsubstituted C₁-C₁₀ alkyl group, a branchedor unbranched, substituted or unsubstituted C₂-C₁₀ alkynyl group, asubstituted or unsubstituted C₂-C₂₀ cycloalkyl group, a substituted orunsubstituted C₂-C₁₀ alkenyl group, and a substituted or unsubstitutedC₆-C₂₀ cycloalkylalkylene group; each R²³ group is independentlyselected from the group consisting of a branched or unbranched,substituted or unsubstituted C₁-C₁₀ alkyl group, a branched orunbranched, substituted or unsubstituted C₂-C₁₀ alkynyl group, asubstituted or unsubstituted C₂-C₁₀ alkenyl group, a substituted orunsubstituted C₂-C₂₀ cycloalkyl group, and a substituted orunsubstituted C₆-C₂₀ cycloalkylalkylene group; R²⁴ is independentlyselected from the group consisting of hydrogen, a branched orunbranched, substituted or unsubstituted C₂-C₁₀ alkynyl group, asubstituted or unsubstituted C₂-C₂₀ cycloalkyl group, a substituted orunsubstituted C₆-C₂₀ cycloalkylalkylene group, a substituted C₅-C₂₀ arylgroup, a substituted or unsubstituted C₆-C₂₀ arylalkylene group, anacetyl group, a substituted or unsubstituted C₃-C₂₀ heterocyclic ringcomprising at least one of O, N, S and Se in the ring; wherein x=1 or 2;y=1 or 2; z=0 or 1; and (x+y+z)=3; wherein each of R¹⁵, R¹⁶, R¹⁸, R¹⁹and R²⁰ independently represent H or optionally substituted C₁-C₄₀carbyl or hydrocarbyl group optionally comprising one or moreheteroatoms; wherein R¹⁷ represents a halogen atom, H or optionallysubstituted C₁-C₄₀ carbyl or C₁-C₄₀ hydrocarbyl group optionallycomprising one or more heteroatoms; wherein k and 1 are independently 0,1 or 2; wherein Ar₁, Ar₂ and Ar₃, which may be the same or different,each represent, independently if in different repeat units, anoptionally substituted C₆₋₄₀ aromatic group (mononuclear orpolynuclear), wherein preferably at least one of Ar₁, Ar₂ and Ar₃ issubstituted with at least one polar or more polarising group; wherein X′is a halogen atom or a cyclic borate group; and wherein Y′ is a halogenatom. 28-29. (canceled)